
Copyright N°. 



COPYRIGHT DEPOSE 



ECONOMIC GEOLOGY 



OF THE 



UNITED STATES 



BY 
HEINRICH RIES, A.M., Ph.D. 

T 



ASSISTANT PROFESSOR OF ECONOMIC GEOLOGY AT 
CORNELL UNIVERSITY 



THE MACMILLAN COMPANY 

LONDON: MACMILLAN & CO., Ltd. 
1905 

All rights reserved 



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Copyright, 1905, 
By THE MACMILLAN COMPANY. 



Set up and electrotyped. Published November, 1905. 



NortoooU -press 

J. S. Cushing & Co. — Berwick & Smith Co. 

Norwood, Mass., U.S.A. 






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I 



ECONOMIC GEOLOGY 

OF THE 

UNITED STATES 



1 



*&%& 



PREFACE 

The following work on the Economic Geology of the 
United States covers essentially the ground which is gone 
over in the elementary course in this subject in Cornell 
University, but it is hoped that -it will prove useful as a 
text-book in other colleges. 

The mode of arrangement is markedly different from that 
found in other books on the same subject, in that the non- 
metallic minerals are discussed first and the metallic minerals 
last. This, to the author, seems the most desirable method 
of treatment, for the reason that the non-metallics are not 
only the most important, the value of their production 
having exceeded the metallics by over one hundred and 
fifty million dollars in 1903, but also because it leads from 
a discussion of the simpler to the more complex forms of 
mineral deposits. 

It has not been thought desirable to include a chapter on 
geologic and physiographic principles, since the space which 
could be allotted to it is altogether too small, and, more- 
over, the study of economic geology presupposes a knowl- 
edge of geology and mineralogy on the. part of the student. 
While the references given at the end of each chapter do 
not include every paper that has been written on the subject 
to which they refer, still it is believed that they are suffi- 
ciently numerous to permit one to follow out the subject in 
considerable detail if he so desire. 

In the preparation of the manuscript all available sources 
of information have been freely drawn upon, and the num- 
bers in parentheses in the text refer to the numbered refer- 
ences at the end of each chapter. 

v 



VI PREFACE 

All statistical figures, unless otherwise stated, are taken 
from the reports of the United States Geological Survey. 

Descriptions of mineral occurrences in foreign countries 
are not included, except in a few cases where the deposits 
serve as an important if not the only source of supply for 
the United States. 

The writer wishes to express his thanks to Professor R. S. 
Tarr for examination and criticism of much of the manu- 
script, and to W. E. McCourt, Instructor in Geology, and 
H. Leighton, Assistant in Geology, for aid in the preparation 
of drawings and statistical tables. For the loan of photo- 
graphs or cuts acknowledgments are due to Messrs. H. F. 
Bain, J. E. Spurr, J. M. Boutwell, G. H. Eldridge, W. Lind- 
gren, F. H. Oliphant, and J. H. Pratt of the United States 
Geological Survey ; Professor A. C. Lane, Michigan Geologi- 
cal Survey ; Dr. D. H. Newland, New York State Museum ; 
Professor C. C. O'Harra, South Dakota School of Mines; 
Professor E. A. Smith, Alabama Geological Survey; Pro- 
fessor G. H. Perkins, Vermont Geological Survey ; Dr. H. B. 
Kummel, New Jersey Geological Survey ; Dr. W. B. Phillips, 
Texas Geological Survey; Dr. G. P. Merrill, United States 
National Museum; also to Messrs. H. W. Turner, F. S. 
Witherbee, A. W. Sheafer, L. Martin, Wiley & Sons, Ver- 
mont Marble Co., and Bedford Quarries Co. 

Cornell University, 
Ithaca, N.Y., June, 1905. 



CONTENTS 

PAGE 

Preface ..... v 

Contents vii 

List of Illustrations . . . . . xv 

List of Abbreviations xxi 

PART I 
NON-METALLIC MINERALS 

CHAPTER I 

Coal 3-38 

Kinds of coal, 3 ; Peat, 3 ; Lignite, 4 ; Bituminous coal, 4 ; Cannel 
coal, 5 ; Semi-bituminous coal, 5 ; Anthracite coal, 5 ; Proximate 
analysis of coal, C ; Origin of coal, 9 ; Conditions of vegetable 
accumulation, 10 ; Chemical changes occurring during coal forma- 
tion, 12 ; Effect of heat and pressure, 14 ; Structural features of 
coal beds, 15 ; Outcrops, 15 ; Associated rocks, 16 ; Variations in 
thickness, 16 ; Other irregularities, 17 ; Coal fields of the United 
States, 18; Geologic distribution of coals in the United States, 10 ; 
Appalachian field, 20 ; Bituminous area, 21 ; Character of Appa- 
lachian bituminous coals, 22 ; Pennsylvania anthracite field, 22 ; 
Rhode Island field, 25 ; The Triassic field, 25 ; Eastern Interior 
field, 26 ; Northern Interior field, 27 ; Western Interior field and 
southwestern fields, 28 ; Western Interior field, 29 ; Southwestern 
field, 20 ; Gulf states lignite area, 30 ; Rocky Mountain fields, 30 ; 
The Pacific Coast fields, 31 ; Alaska, 32 ; Production of coal, 33 ; 
Production of coke, 35 ; References on coal, 35 ; References on 
peat, 38. 

CHAPTER II 

Petroleum, Natural Gas, and Other Hydrocarbons . . 39-68 

History of petroleum development, 39 ; History of natural gas 

development, 40 ; Properties of petroleum, 40; Properties of natural 

gas, 42 ; Mode of occurrence, 43 ; Pressure of oil and gas wells, 44 ; 

Origin, 46 ; Inorganic theory, 46 ; Organic theory, 47 ; Geological 



Vlll CONTENTS 

PAGE 

distribution of petroleum and natural gas, 48 ; Distribution of 
petroleum in the United States, 48 ; Appalachian field, 48 ; Ohio- 
Indiana field, 50 ; Texas-Louisiana oil fields, 51 ; Kansas, 52 ; Cali- 
fornia, 52 ; Wyoming, 53 ; Colorado, 53 ; Alaska, 54 ; Distribution 
of natural gas in the United States, 54 ; New York, 54 ; Pennsyl- 
vania, 54 ; West Virginia, 55 ; Ohio, 55 ; Indiana, 55 ; Kansas, 55 ; 
Uses of petroleum, 56 ; Uses of natural gas, 56 ; Oil shales, 56 ; 
Solid bitumens, 57 ; Occurrence, 57 ; Asphaltites, 58 ; Albertite, 
59 ; Anthraxolite, 59 ; Ozokerite, 59 ; Grahamite, 59 ; Lake asphalt, 
59 ; Uintaite or gilsonite, 59 ; Manjak, 59 ; Bituminous rocks, 60 ; 
Analyses, 60 ; Uses, 61 ; Production of petroleum, natural gas, 
and asphaltum, 61 ; Eeferences on petroleum, 66 ; References on 
natural gas, 67 ; References on oil shale, 67 ; References on as- 
phaltum, 67. 

CHAPTER III 

Building Stones 69-91 

Properties of building stones, 69 ; Color, 70 ; Texture, 70 ; Den- 
sity, 70 ; Hardness, 71 ; Strength, 71 ; Crushing strength, 72 ; 
Transverse strength, 72 ; Porosity and ratio of absorption, 73 ; 
Resistance to frost, 73 ; Resistance to heat, 73 ; Structural features 
affecting quarrying, 74 ; Bedding planes, 74 ; Granites, 75 ; Char- 
acteristics of granites, 75 ; Distribution of granites in the United 
States, 76 ; Eastern crystalline belt, 77 ; Central states, 77 ; West- 
ern states, 77 ; Uses of granite, 77 ; Miscellaneous igneous rocks, 
78 ; Limestones and marbles, 78 ; General characteristics, 78 ; 
Varieties of limestones, 79 ; Distribution of limestones in the 
United States, 80 ; Distribution of marbles in the United States, 
81 ; Onyx marbles, 83 ; Serpentine, 83 ; Sandstones, 84 ; General 
properties, 84 ; Varieties of sandstone, 85 ; Distribution of sand- 
stones in the United States, 86 ; Uses of sandstones, 87 ; Slates, 
87 ; General characteristics, 87 ; Distribution of slates in the 
United States, 88 ; Uses of slate, 89 ; Production of building 
stones, 89 ; References on building stones, 90 ; References on 
onyx marble, 91. 

CHAPTER IV 

Clay 92-108 

Definition, 92 ; Residual clays, 92 ; Sedimentary clays, 93 ; 
Marine clays, 94 ; Elood-plain clays, 94 ; Lake clays, 94 ; Glacial 
clays, 94 ; iEolian clays, 94 ; Properties of clay, 95 ; Chemical 
properties, 95 ; Physical properties, 96 ; Plasticity, 96 ; Tensile 
strength, 96 ; Shrinkage, 96 ; Fusibility, 97 ; Specific gravity, 97 ; 



CONTEXTS IX 



Chemical composition, 97 ; Classification of clay, 98 ; Kinds of 
clay, 99 ; Geological distribution, 100 ; Distribution of clays in the 
United States by kinds, 100 ; Kaolins, 100 ; Fire clays, 102 ; Pot- 
tery clays, 103 ; Brick and tile clays, 104 ; Miscellaneous clays of 
importance, 104 ; Uses of clay, 105 ; Production of clay, 105 ; 
Eeferences on clay, 106. 

CHAPTER V 

Lime and Calcareous Cements 109-123 

Composition of limestone, 109 ; Changes in burning, 110 ; Lime, 
110; Hydraulic cements, 111; Pozzuolano cements, 111; Hy- 
draulic limes, 112 ; Natural rock cements, 112 ; Portland cement, 
113 ; Distribution of lime and cement materials in the United States, 
116 ; Limestone for lime. 116 ; Hydraulic limes. 117 ; Natural rock 
cement, 117 ; Portland cements, 118 ; Uses of lime, 119 ; Uses of 
cement, 119 ; Production of cement, 120 ; References on lime and 
cement materials, 121. 

CHAPTER VI 

Salines 124-138 

Salt, 124 ; Occurrence of salt in sea and lake waters. 124 ; Rock 
salt, 125 ; Origin of rock salt, 125 ; Natural brines, 127 ; Salt 
marshes and soils, 127 ; Distribution of salt in the United States, 
127; New York. 127; Michigan. 129; Other eastern states, 129; 
Louisiana, 129 ; Kansas, 130 ; Other western states, 130 ; Extrac- 
tion, 131 ; Uses, 132 ; Production of salt. 132 ; References on salt. 
134; Borax, 134; Borax minerals, 134; Distribution in United 
States, 134 ; Uses, 134 ; Production of borax, 136 ; References on 
borax, 136; Sodium sulphate, 136; References, 137; Sodium car- 
bonate, 137 ; References, 137 ; Soda niter, 137 ; References, 138. 

CHAPTER VII 

Gtpsum 139-146 

Gypsum, 139 ; Anhydrite, 139 ; Origin of gypsum, 139 ; Gypsite, 

140 ; Distribution in the United States, 140 ; Iowa. 140 ; Kansas, 

141 ; Michigan, 142 ; New York, 142 ; Other occurrences, 142 ; 
Analyses, 143 ; Uses, 143 ; Production of gypsum, 145 ; References 
on gypsum, 146. 

CHAPTER VIII 

Fertilizers 147-157 

Phosphate of lime, 147 ; Apatite, 147 ; Amorphous phosphates. 
147 ; Florida phosphates, 148 ; Land pebble or matrix rock, 149 ; 



CONTENTS 



PAGE 

River pebble, 149 ; South Carolina phosphates, 150 ; Tennessee 
phosphates, 150 ; Other phosphate occurrences, 153; Composition, 
153 ; Uses, 154 ; Guano, 155 ; Greensand, 155 ; Production, 156 ; 
References on fertilizers, 157. 



CHAPTER IX 

Abrasives 158-166 

Introductory, 158 ; Grindstones, 158 ; Whetstones and oilstones, 
159 ; Buhrstones and millstones, 161 ; Pumice and volcanic ash, 
161 ; Infusorial earth and tripoli, 162 ; Crystalline quartz, 163 ; 
Garnet, 163 ; Corundum and emery, 163 ; Artificial abrasives, 165 ; 
Production of abrasives, 165 ; References on abrasives, 166. 



CHAPTER X 

Minor Minerals 167-203 

Asbestos, 167 ; Asbestos minerals, 167 ; Distribution, 167 ; Uses, 
169 ; Production of asbestos, 169 ; References on asbestos, 169 ; 
Barite, 170 ; Uses, 170 ; Production, 170 ; References on barite, 
171 ; Fluorspar, 171 ; Distribution in United States, 172 ; Uses, 173 ; 
References on fluorspar, 174; Fuller's earth, 174; Production of 
fuller's earth, 176 ; References on fuller's earth, 176 ; Glass sand, 
176 ; References on glass sand, 178 ; Graphite, 178 ; Distribution 
of graphite in the United States, 178 ; Uses, 179 ; Production of 
graphite, 180 ; References on graphite, 181 ; Lithographic stone, 
181; References on lithographic stone, 183; Lithium, 183; Mag- 
nesite, 183 ; References on magnesite, 184 ; Mica, 184 ; References 
on mica, 186 ; Mineral pigments, 186 ; Hematite, 186 ; Ochers, 186 ; 
Slate, 187 ; Gypsum, 187 ; Barite, 187 ; Asbestos, 188 ; Graphite, 
188 ; Calcium carbonate, 188 ; Other paints, 188 ; Production of 
mineral pigments, 189 ; References on mineral paints, 189 ; Mold- 
ing sand, 189 ; References on molding sand, 190 ; Monazite, 190 ; 
Uses, 191 ; Production of monazite, 191 ; References on monazite, 
191 ; Precious stones, 192 ; Diamond, 192 ; Ruby, 193 ; Sapphire, 
193; Emerald, 193; Topaz, 194; Turquoise, 194; Garnet, 194; 
Opal, 195 ; Other precious stones, 195 ; Production of precious 
stones, 195 ; References on precious stones, 196 ; Sulphur and 
pyrite, 196 ; Sulphur, 196 ; Solfataric type, 196 ; Gypsum type, 197 ; 
Uses, 198 ; Production of sulphur, 198 ; References on sulphur, 
199; Pyrite, 199; Distribution, 199; Uses, 200; References on 
pyrite, 200 ; Strontium, 200 ; Uses, 201 ; References on strontium, 
201 ; Talc and soapstone, 201 ; Uses, 202 ; Pyrophyllite, 203 ; 
Production, 203 ; References on talc and soapstone, 203. 



CONTENTS XI 



CHAPTER XI 

PAGE 

Water 204-212 

Mineral waters, 204 ; Distribution of mineral waters in the 
United States, 205 ; Production of mineral waters, 206 ; References 
on mineral waters, 207 ; Underground waters, 207 ; Ground water, 
207 ; Artesian waters, 209 ; References on underground water, 211. 



CHAPTER XII 

Soils and Road Materials 213-219 

Soils, 213 ; Origin, 213 ; Residual soils, 213 ; Transported soils, 
213 ; Properties of soils, 213 ; Chemical properties, 214 ; Physical 
properties, 215 ; Distribution of soils in the United States, 216 ; 
References on soils, 216 ; Road materials, 217 ; References on road 
materials, 219. 



PART II 
METALLIC MINERALS OR ORES 

CHAPTER XIII 

Ore Deposits 223-250 

Definition, 223 ; Gangue minerals, 223 ; Origin of ore bodies, 
224 ; Ores of contemporaneous origin, 224 ; Concentration of ores 
in rocks, 225 ; Formation of cavities, 231 ; Precipitation of metals 
from solution, 232 ; Replacement or metasomatism, 233 ; Concen- 
tration by eruptive after-action or pneumatolysis, 234 ; Other 
causes of precipitation, 235 ; Forms of ore bodies, 236 ; Fissure 
veins, 236 ; Other forms of ore deposits, 241 ; Secondary changes 
in ore deposits, 242 ; Weathering or superficial alteration, 242 ; 
Secondary deposition below water level, 244 ; Value of ores, 245 ; 
Classification of ore deposits, 246 ; References on ore deposits, 249. 



CHAPTER XIV 

Iron 251-277 

Ores of iron, 251 ; Magnetite, 254 ; Distribution of magnetites in 
the United States, 254 ; Non-titaniferous magnetites, 254 ; Other 
occurrences, 254 ; Titaniferous magnetites, 257 ; Magnetite sands, 
258 ; Hematite, 259 ; Distribution of hematite ores in the United 
States, 259 ; Lake Superior region, 259 ; Clinton ore, 266 ; Other 



Xll CONTENTS 



PAGE 

hematite occurrences, 268 ; Limonite, 269 ; Bog ores, 269 ; Residual 
limonites, 270 ; Other occurrences, 271 ; Siderite, 272 ; Production 
of iron ores, 273 ; References on iron ores, 276. 



CHAPTER XV 

Copper 278-302 

Ores, 278 ; Impurities in copper ores, 280 ; Superficial alteration 
of copper ores, 280 ; Distribution of copper ores in the United 
States, 281 ; Montana, 282 ; Michigan, 287 ; Arizona, 290 ; Bisbee 
or Warren district, 290 • Jerome district, 292 : Clifton district, 293 ; 
Globe district, 294 ; Appalachian region, 294 ; Utah, 296 ; Cali- 
fornia, 297 ; Other occurrences, 298 ; Uses of copper, 298 ; Produc- 
tion of copper, 299 ; References on copper, 301. 



CHAPTER XVI 

Lead and Zinc 303-324 

Ores of lead, 303 ; Ores of zinc, 303 ; Superficial alteration of 
lead and zinc ores, 305 ; Distribution of lead and zinc ores in the 
United States, 305 ; Lead alone, 306 ; Appalachian belt, 306 ; South- 
eastern Missouri, 306 ; Desilverized lead, 307 ; Zinc ores alone, 
307 ; Eastern and southern states, 308 ; Sussex County, N.J., 308 ; 
Virginia and Tennessee, 310 ; Pennsylvania, 311 ; Lead and zinc 
ores of the Mississippi Valley region, 311 ; Upper Mississippi Valley 
area, 311 ; Ozark region, 314 ; Origin of the ores, 316 ; Rocky 
Mountain states, 318 ; Uses of lead and zinc, 319 ; Uses of lead, 
319 ; Uses of zinc, 320 ; Production of lead and zinc, 321 ; Refer- 
ences on lead and zinc, 323. 



CHAPTER XVII 

Gold and Silver .......... 325-363 

Ores of gold, 325 ; Ores of silver, 325 ; Mode of occurrence, 326 ; 
Weathering and secondary enrichment, 327 ; Classification, 327 ; 
Geological distribution, 329 ; Extraction, 329; Distribution of gold 
and silver ores, 331 ; Cordilleran region, 332 ; Pacific coast Creta- 
ceous gold-quartz ores, 332 ; Mother Lode belt, 333 ; Nevada 
County, 334 ; Central belt of gold-silver ores, 335 ; Mercur, Utah, 
336 ; Other occurrences, 337 ; Eastern belt of Tertiary gold-silver 
veins, 337 ; Cripple Creek, 338 ; San Juan region, 341 ; Tonopah, 
Nev. , 343 ; Comstock Lode, Nev. , 344 ; Other occurrences, 345 ; 
Auriferous gravels, 346 ; Black Hills region, 350 ; Homestake belt, 



CONTENTS Xlll 

PAGE 

351 ; Siliceous Cambrian ores, 852 ; Michigan region, 352 ; Eastern 
crystalline belt, 352 ; Alaska, 353; Uses of gold, 357 ; Uses of silver, 
358 ; Production of gold and silver, 358 ; References on gold and 
silver, 360. 

CHAPTER XVIII 

Silver-Lead 364-374 

Silver-lead ores, 364 ; Lead ville District, Colo., 364 ; Aspen, Colo., 
367 ; Other occurrences, 369 ; Park City, Utah. 370 ; Tintic District, 
Utah, 372 ; Cceur d'Alene, Ido., 372 ; Montana, Nevada, etc., 373 ; 
References on silver-lead ores, 374. 

CHAPTER XIX 

Aluminum, Manganese, and Mercury 375-395 

Ores of aluminum, 375 ; Distribution of bauxite in the United 
States, 376 ; Georgia-Alabama, 877 ; Arkansas, 378 ; New Mexico, 
379 ; Uses of aluminum, 379 ; Uses of bauxite, 380 ; Production 
of bauxite and aluminum, 380 ; References on bauxite and alumi- 
num, 383 ; Manganese, 383 ; Manganese ores, 383 ; Origin, 384 ; 
Distribution of manganese ores in the United States, 384 ; Eastern 
area, 885 ; Arkansas, 387 ; Other United States occurrences, 387 ; 
Uses of manganese, 388 ; Production of manganese, 388 ; Refer- 
ences on manganese, 390 ; Ores of mercury, 390 ; Mode of occur- 
rence, 390 ; Distribution in the United States, 390 ; California, 391 ; 
Texas, 392 ; Origin, 393 ; Uses of mercury, 393 ; Production of 
mercury, 394 ; References on mercury, 395. 



CHAPTER XX 

Minor Metals 396-417 

Ores of antimony, 396 ; Distribution of antimony in the United 
States, 396 ; Uses, 397 ; Production of antimony, 397 ; References 
on antimony, 397 ; Arsenic, 398 ; References on arsenic, 398 ; Bis- 
muth, 399 ; Ores, 399 ; Distribution, 399 ; Uses and production, 

399 ; Ores of chromic iron, 399 ; Origin of chromite, 400 ; Analyses, 

400 ; Distribution of chromic iron in United States, 400 ; Uses, 401 ; 
Production of chromite, 402 ; References on chromic iron ore, 402 ; 
Molybdenum, ores and occurrences, 403 ; Uses of molybdenum, 
403 ; Production of molybdenum, 403 ; References on molybdenum, 
403 ; Nickel and cobalt, 403 ; Ores, 403 ; Distribution, 404; Eastern 
occurrences of nickel, 404 ; Other occurrences, 405 ; Uses of nickel, 
405 ; Uses of cobalt, 406 ; Production, 406 ; References on nickel 



XIV CONTENTS 

and cobalt, 407; Platinum group of metals, 407; Platinum, 407; 
Distribution in the United States, 407 ; Uses of platinum, 408 ; Pro- 
duction of platinum, 408 ; References on platinum, 409 ; Palladium, 
409 ; Osmium, 409 ; Iridium, 410 ; Tin, 410 ; Ores, 410 ; Mode of 
occurrence, 410 ; Distribution in the United States, 411 ; Uses of 
tin, 412 ; Production of tin, 412 ; References on tin, 413 ; Titanium, 
413 ; Ores, 413 ; Occurrence, 413 ; Uses, 414 ; References on tita- 
nium, 414 ; Tungsten, 414 ; Ores, 414; Occurrence, 415 ; Uses, 415 ; 
Production, 415 ; References on tungsten, 416 ; Uranium and vana- 
dium, 416 ; Ores, 416 ; Uses, 416 ; Production, 416 ; References on 
uranium and vanadium, 417. 



LIST OF ILLUSTRATIONS 

FIG. PAGE 

1. Diagram showing changes occurring in passage of vegetable tissue 

to graphite 13 

2. Section in coal measures of western Pennsylvania, showing fire 

clay under coal beds 16 

3. Section showing irregularities in coal seam, a, split ; b, parting of 

shale ; c, pinch ; d, swell ; e, cut out 17 

4. Section of faulted coal seam 17 

5. Section across Coosa, Ala. , coal field, showing folding and faulting 

characteristic of southern end of Appalachian coal field . . 20 

6. Map of Pennsylvania anthracite field 23 

7. Sections in Pennsylvania anthracite field 24 

8. Coal breaker in Pennsylvania anthracite region .... 25 

9. Section across Eastern Interior coal field 26 

10. Shaft house and tipple, bituminous coal mine, Spring Valley, 111. . 27 

11. Generalized section of Northern Interior coal field .... 28 

12. Composite section showing structure of lower coal measures in Iowa 29 

13. Section of anticlinal fold showing accumulation of gas, oil, and 

water 43 

14. Map showing oil and gas fields of United States .... 49 

15. Geological section in Ohio-Indiana oil and gas field ... 50 

16. Section of Spindle Top oil field near Beaumont, Tex. ... 51 

17. Section in Los Angeles oil field 53 

18. Map of asphalt and bituminous rock deposits of United States . 58 

19. Section of Gilsonite vein, Utah 59 

20. Map showing distribution of crystalline rocks (mainly granite) in 

United States 76 

21. Map showing marble areas of eastern United States ... 81 

22. Section showing cleavage and bedding in slate .... 87 

23. Section in slate quarry with cleavage parallel to bedding, a, purple 

slate ; 6, unworked ; c and d, variegated ; e and /, green ; 

g and h, gray green ; j, quartzite ; j, gray with black patches . 88 

24. Section showing formation of residual clay 93 

25. Section of a sedimentary clay deposit 93 

26. Map showing distribution of salt-producing areas in United States, 

compiled from various geological survey reports . . . 128 

27. Map showing gypsum-producing localities of United States . . 141 

28. Map of Florida phosphate deposits 148 

29. Map of Tennessee phosphate areas 151 

xv 



XVI LIST OF ILLUSTRATIONS 



FIG 



PAGE 

30. Vertical section showing geologic position of Tennessee phosphates 152 

31. Map showing distribution of abrasives in United States . . . 159 

32. Section showing occurrence of corundum around border of dunite 

mass . 164 

33. Asbestos vein in serpentine . . 168 

34. Ideal section across a river valley, showing the position of ground 

water and the undulations of the water table with reference to 

the surface of the ground and bed rock 208 

35. Geologic section of Atlantic Coastal Plain, showing water-bearing 

horizons 210 

36. Section from Black Hills across South Dakota, showing artesian 

well conditions 211 

37. Replacement vein in syenite rock, War Eagle mine, Rossland, B.C. 

a, granular orthoclase with a little sericite ; b, secondary biotite ; 

q, secondary quartz ; c, chlorite ; black, secondary pyrrhotite 234 

38. Section of vein in Enterprise mine, Rico, Colo. The right side 

shows later banding due to reopening of the fissure . . . 237 

39. Section showing change in character of vein passing from gneiss (g) 

to soft shale (jp) 238 

40. Tabulation of strikes of principal veins in Monte Cristo, Wash., 

district 239 

41. Linked veins 240 

42. Gash vein with associated "flats" and "pitches" — Wisconsin 

zinc region 240 

43. Section at Bonne Terre, Mo., showing ore disseminated through 

limestone 241 

44. Section through Copper Queen mine, Bisbee, Ariz., showing varia- 

ble depth of weathering 243 

45. Map showing distribution of iron ores in United States . . . 253 

46. Map of Lake Superior iron regions, shipping ports, and transporta- 

tion lines 259 

47. Sections of iron ore deposits in Marquette range .... 260 

48. Generalized vertical section through Penokee-Gogebic ore deposit 

and adjacent rocks, Colby mine, Bessemer, Mich. . . . 261 

49. Generalized vertical section through Mesabi ore deposit and adja- 

cent rocks 262 

50. Section of Clinton ore beds, Oxmoor, Ala. a, red sandstone, 5' ; 

6, yellow sandstone, 6' ; c, red sandstone, 15' ; d, ore, 22', 
upper 2' soft ; e, shale, 6' ; /, rich ore, 2' 6" . . . . 266 

51. Section illustrating formation of residual limonite in limestone . 270 

52. Map showing distribution of copper ores in United States . . 282 

53. Map of Butte, Mont., district, showing distribution of veins and 

geology 283 

54. Section at Butte, Mont., showing mode of occurrence of the ore . 284 



LIST OF ILLUSTRATIONS XV11 

FIG. PAGE 

55. Section across Keweenaw Point . .... 287 

56. Section showing occurrence of amygdaloidal copper, Quincy mine, 

Michigan 288 

57. Geological section at Bisbee, Ariz 291 

58. Generalized section of ore bodies at Bisbee, Ariz 292 

59. Section of Morenci district. P, porphyry ; S, unaltered sediments ; 

F, fissure veins ; M, metamorphosed limestone and shale ; 

O, contact metamorphic ores ; R, disseminated chalcocite . 293 

60. Section of ore body at Bully Hill, Calif 298 

61. Map showing distribution of lead and zinc ores in United States . 305 

62. Generalized section of southeastern Missouri lead region . . 306 

63. Model of Franklin zinc-ore body 309 

64. Section of Bertha zinc mines, Wythe County, Va., showing irregu- 

lar surface of limestone covered by residual clay bearing ore . 310 

65. Section showing occurrence of lead and zinc ores in Wisconsin, 

with fissure ore in flats and pitches, and disseminated ore in 

oil rock 312 

66. Map of Ozark region 314 

67. Generalized section showing occurrence of lead and zinc ore in 

southwestern Missouri 315 

68. A typical hoisting outfit in the southwestern Missouri zinc region . 316 

69. Map showing distribution of gold and silver ores in United States . 331 

70. Map and section of portion of Mother Lode district, Calif. Pgv, 

river gravels, usually auriferous ; Ng, auriferous river gravels. 
Sedimentary rocks : Jm, inariposa formation (clay, slate, sand- 
stone, and conglomerate) ; Cc, calaveras formation (slaty 
mica schists). Igneous rocks : Nl, latite ; Nat, andesite tuffs, 
breccia, and conglomerate ; mdi, meta-diorite; Sp, serpentine ; 
ma, meta-andesite ; ams, amphibole schist .... 334 

71. Section illustrating relations of auriferous quartz veins at Nevada 

City, Calif 335 

72. Section at Mercur, Utah 336 

73. Map of Colorado showing location of mining regions . . . 338 

74. Section of vein at Cripple Creek, Colo 339 

75. Geologic map of Telluride district, Colorado, showing outcrop of 

more important veins 342 

76. Ideal cross section of rocks at Tonopah, Nev 343 

77. Section of Comstock Lode. D, diorite ; Q, quartz ; V, vein matter 

in earlier diabase (Db) ; H, earlier hornblende andesite ; 

A, augite andesite * 344 

78. Generalized section of old placer, with technical terms, a, volcanic 

cap ; b, upper lead ; c, bench gravel ; d, channel gravel . . 347 

79. Section of Homestake Belt at Lead, S.D., showing relation of 

ancient and modern placers to Homestake Lode . . . 350 



XV111 LIST OF ILLUSTRATIONS 

FIG. PAGE 

80. Typical section of siliceous gold ores, Black Hills, S.D. . . . 351 

81. Map showing mineral deposits of Alaska as far as known . . 354 

82. Sketch map of Douglas Island, Alaska 355 

83. Cross section through Alaska Treadwell mine on nonhern side of 

Douglas Island 356 

84. Ideal section across Leadville district 366 

85. Section of ore body at Aspen, Colo. 368 

86. Diagrammatic section across a northeasterly lode at Rico, Colo., 

showing " blanket " of ore 369 

87. Vein filling a fault fissure, Enterprise mine, Rico, Colo. . . 370 

88. Section of lead-silver vein, Cceur d'Alene, Ido 373 

89. Geologic map of Alabama-Georgia bauxite region .... 377 

90. Section of bauxite deposit, a, Residual mantle ; 6, Red sandy clay 

soil; c, Pisolitic ore; d, Bauxite with clay; e, Clay with 

bauxite ; /, Talus ; g, Mottled clay ; h, Drainage ditch . . 378 

91. Map showing Georgia manganese areas 385 

92. Section in Georgia manganese area showing geologic relations of 

manganese, limonite, and ocher 386 

93. Section of Batesville, Ark., manganese region, illustrating geological 

structure and relation of different formations to marketable 

and non-marketable ore 387 

94. Map of California mercury localities 391 

95. Map showing Texas mercury region 392 

96. Section of cinnabar vein in limestone, Terlingua, Tex. . . . 393 

97. Sketch map showing location of Carolina tin belt .... 411 



PLATES 



PLATE PAGE 

I. Map showing distribution of coal in United States. Frontispiece 
II. Fig. 1. Pit working (stripping) near Milnesville, Pa. The 

mammoth seam is uncovered in bottom of pit . . . 31 
Fig. 2. Lignite seam, Williston, N.D 31 

III. Fig. 1. General view of Tuna Valley, in Pennsylvania oil field 48 
Fig. 2. View in Los Angeles, Calif., oil field. Such close spac- 
ing of oil derricks tends to hasten the exhaustion of the 

oil supply 48 

IV. General view of Spindle Top oil field, Beaumont, Tex. . . 51 
V. Fig. 1. Quarry of bituminous sandstone, Santa Cruz, Calif. . 60 

Fig. 2. Granite quarry, Hard wick, Vt 60 

VI. Quarry in limestone, Bedford, Ind. 80 

VII. Marble quarry, Proctor, Vt 82 - 

VIII. View of green slate quarry, Pawlet, Vt 88 / 

IX. Bank of sedimentary clay, Woodbridge, N.J. This section 

affords at least five kinds of clay 103 ' 

X. Fig. 1. Quarry of natural cement rock, Cumberland, Md. . 117 
Fig. 2. Marl pit at Warners, N.Y. The dark streaks are 

peat and the marl is underlain by clay . . . .117 

XI. Fig. 1. Interior view of salt mine, Livonia, N.Y. . . . 12!) 

Fig. 2. Borax mine near Daggett, Calif. .... 129 

XII. Fig. 1. Gypsum quarry, Alabaster, Mich. Shows gypsum 
overlain by glacial drift, The dump in foreground is over- 
burden removed from gypsum ...... 139 

Fig. 2. Rock phosphate mine near Ocala, Fla. . . . 139 

XIII. Fig. 1. Grindstone quarry, Tippecanoe, Ohio .... 159 
Fig. 2. Corundum vein between peridotite and gneiss, Corun- 
dum Hill, Ga 159 

XIV. Fig. 1. View of open cut in magnetite deposit, Mineville, N.Y. 

The pillars are ore left standing to support the gneiss 

hanging wall ......... 254 

Fig. 2. General view of magnetic separating plants and shaft 

houses, Mineville, N.Y 254 

XV. Fig. 1. Iron mine, Soudan, Minn. Shows old open pit with 

jasper horse in middle 261 

Fig. 2. Outcrop of Clinton iron ore, Red Mountain, near 

Birmingham, Ala 261 



XX 



PLATES 



PLATE 

XVI. 



XVII. 



XVIII. 
XIX. 



XX. 



XXI. 



XXII. 



XXIII. 
XXIV. 



XXV. 



PAGB 

General view of Mountain Iron mine, Mesabi Eange, Minn. 

Shows mining of ore with steam shovels and covering 

of (a) glacial drift 264 

Fig. 1. Pit of residual limonite, Shelby, Ala 270 I 

Fig. 2. Old limonite mine, Ivanhoe, Va., showing pinnacled 

surface of limestone which underlies the ore-bearing clay. 

The level of surface before mining began is seen on either 

side of excavation 270 

Anaconda group of mines, Butte, Mont 285 

Fig. 1. Smelter of Clifton Copper Co., Clifton, Ariz. . . 293 , 

Fig. 2. View of Bingham Canon, Utah 293 

Fig. 1. Kennedy mine on the Mother Lode near Jackson, 

Calif 333/ 

Fig. 2. Auriferous quartz veins in Maryland mine, Nevada 

City, Calif 333 

Fig. 1. View of Independence mine and Battle Mountain, 

Cripple Creek, Colo 340 

Fig. 2. General view of region around Tonopah, Nev. . . 340 
Fig. 1. Hydraulic mining of auriferous gravel. The sluice 

box in foreground is for catching the gold .... 348 

Fig. 2. An Alaskan placer deposit 348 

Homestake mills, hoists and open cuts at Lead, S.D. . . 351 
Fig. 1. General view of Rico, Colo., and Enterprise group of 

mines 369 

Fig. 2. Ontario mine, Park City, Utah 369 

Fig. 1. Bauxite bank, Rock Run, Ala 376 

Fig. 2. Furnace for roasting mercury ore, Terlingua, Tex. . 376 



ABBREVIATIONS USED 

In the references at the end of each chapter, the volume numbers are given 

in Roman numerals. Numbers following a : indicate page numbers. 

The date of publication follows these, and is separated from them by a 

comma. 
Ala. Ind. and Sci. Soc, Proc. — Alabama Industrial and Scientific Society, 

Proceedings. 
Amer. Geol. — American Geologist. 
Amer. Inst. Min. Eng., Trans. — American Institute Mining Engineers, 

Transactions. 
Amer. Jour. Sci — American Journal of Science. 
Col. Sci. Soc, Proc. — Colorado Scientific Society, Proceedings. 
Eng. and Min. Jour. — Engineering and Mining Journal. 
Geol. Soc. Amer., Bull. — Geological Society of America, Bulletin. 
Jour. Geol. — Journal of Geology. 
Min. and Met. — Mining and Metallurgy. 
Min. and Sci. P. — Mining and Scientific Press. 
Min. Indus. — Mineral Industry. 
Min. Mag. — Mining Magazine. 
Mo. Geol. Surv. — Missouri Geological Survey. 

JV. Y. Acad. Sci., Trans. — New York Academy of Science, Transactions. 
JSf. Ca. Geol. Surv. — North Carolina Geological Survey. 
Sch. M. Quart. — School of Mines Quarterly. 

U. S. Geol. Surv., Mon. — United States Geological Survey, Monograph. 
U. S. Geol. Surv., Ann. Eept. — United States Geological Survey, Annual 

Report. 
Zeitsch. f. Prak. Geol. — Zeitschrift fur Praktische Geologic 



xxi 



PART I 

NON-METALLIC MINERALS 



CHAPTER I 
COAL 

Kinds of Coal. — There is such an intimate gradation be- 
tween vegetable accumulation now in process of formation 
and mineral coal that it is generally admitted that coal is of 
vegetable origin. By a series of slow changes (p. 12), the 
vegetable remains lose water and gases, the carbon becomes 
concentrated, and the materials assume the mineralized ap- 
pearance of coal. To the stages of this process names are 
given, four of which — peat, lignite, bituminous coal, and 
anthracite coal — are commonly known. 

Peat (79-83). — This, which may represent the first stage 
in coal formation, is formed chiefly by the growth of 
the bog moss, sphagnum, in moist places. A section in a 
peat bog, from the top downward, shows : (1) a layer 
of living moss, and other plants ; (2) a layer of dead 
moss fibers, whose structure is clearly recognizable, and 
which grades into (3) a layer of fully formed peat, a 
dense brownish black mass, in which the vegetable struc- 
ture is often indistinct. 

The following analyses show the difference in composition 
of the different layers. They also show that while during 
this change the hydrogen and oxygen diminish, the carbon 
increases in proportion. 



ECONOMIC GEOLOGY OF THE UNITED STATES 



Material 



Carbon 



Hydrogen 



Oxygen 



Nitrogen 



Sphagnum 

Porous, light brown sphag- 
num peat 

Porous, red brown peat . . 
Heavy brown peat . . . . 
Heavy black peat . . . . 



49.88 

50.86 
53.51 
56.43 
59.7 



6.54 

5.8 
5.9 
5.32 

5.7 



42.42 



1.16 



42.57 

40.59 

38.25 
33.04 I 1.56 



Lignite. — This substance, also called brown coal, repre- 
senting the second stage in coal formation, is brownish black 
or black in color, and often shows a brilliant luster, conchoidal 
fracture, and brown streak. Where the lumps have formed 
from trunks or other large, woody masses, the vegetable 
structure is often clearly visible. It burns readily, but with 
a long, smoky flame, and hence with lower heating power 
than the true coal. Because of the large amount of mois- 
ture, it often dries out on exposure to the air, and rapidly 
disintegrates to a powdery mass. 

The lignites have been found in the more recent geological periods. 
Because of the greater age and the greater compression of the vegetable 
matter, due to the pressure of overlying strata, lignite resembles true 
coal more closely than peat. In fact, in favorable situations, the altera- 
tion of Tertiary and Cretaceous coals has proceeded as far as to trans- 
form them beyond the stage of lignite. 

Jet is a coal-black variety of lignite, with resinous luster and sufficient 
density to permit its being carved into small ornaments. It is obtained 
on the Yorkshire coast of England, where a single seam produced 5180 
pounds, valued at $1250. According to Phillips, jet is simply a conif- 
erous wood, still showing the characteristic structure under the micro- 
scope. (" Geology of England and Wales," p. 278.) 

Bituminous Coal. — This represents the third stage in coal 
formation. It is denser than lignite, deep black, compara- 



COAL 5 

tively brittle, and breaks with cubical, or sometimes con- 
choidal, fracture. On superficial inspection it usually shows 
no trace of vegetable remains ; but in thin sections examined 
under the microscope, traces of woody fiber, lycopod spores, 
etc., are commonly seen. Bituminous coal burns readily, 
with a smoky flame of yellow color, but with much greater 
heating power than lignite. It does not disintegrate on ex- 
posure to air as readily as lignite does. Most bituminous 
coal is of earlier age than lignite ; but where the two occur 
in the same formation, as in parts of the West, the lignite 
is commonly in horizontal strata, while the bituminous coal 
occurs in areas of at least slight disturbance. 

When freed of their volatile hydrocarbons and other gaseous constitu- 
ents by heating to redness in an oven, many bituminous coals cake to a 
hard mass called coke. Since some bituminous coals do not possess this 
characteristic, it is customary to divide these coals into coking and non- 
coking coals. 

Cannel coal is a compact variety of non-coking bituminous 
coal with a dull luster and conchoid al fracture. Owing to 
its unusually high percentage of volatile hydrocarbons, upon 
which its chief value depends, cannel coal ignites easily, 
burning with a yellow flame. (See analysis No. 14.) 

Semi-bituminous is a name applied to certain varieties in- 
termediate between bituminous and anthracite coal. 

Anthracite Coal. — This coal is black, hard, and brittle, 
with high luster and conchoidal fracture. It represents the 
last stage in the formation of coal, and shows no traces 
of vegetable structure within its mass, although plant 
impressions are often abundant in the rocks immediately 
above and below it. Anthracite has a lower percentage 
of volatile hydrocarbons and higher percentage of fixed 



6 



ECONOMIC GEOLOGY OF THE UNITED STATES 



carbons than any of the other varieties (p. 8). On this 
account, it ignites much less easily and burns with a short 
flame, but gives great heat. 

The geological distribution of anthracite is more restricted 
tiian that of bituminous coal and, in fact, its occurrence 
is often more or less intimately connected with dynamic 
disturbances. 

Proximate Analysis of Coal. — An elementary analysis of 
coal (see p. 14) is of comparatively little practical value. 
Therefore proximate analyses are commonly employed, in 
which the probable method of combination of the elements 
is given. By the proximate method the elements in the 
coal are grouped as moisture, volatile hydrocarbons, fixed 
carbon, ash, and sulphur. 

The following table gives the proximate analysis of a 
number of coals from all parts of the United States. The 
analyses are arranged in the following order: Peat, Lignite, 
Bituminous Coal, Anthracite. 

Proximate Analyses of Coal 



Locality 


Moisture 


Volatile 
Hydro- 
carbon 


Fixed 
Carbon 


Ash 


Sulph. 


Fuel 
Ratio 


1. Peat 


20.22 


52.31 


24.52 






.47 


Dismal Swamp 














2. Newcastle .... 


13.59 


32.31 


48.32 


5.78 


.164 


1.49 


Washington 














3. Kootznaboo . . . 


2.41 


44.75 


47.93 


4.88 


.67 


1.07 


Alaska 














4. Rockdale .... 


33.63 


46.78 


7.45 


12.14 


.99 


.15 


Texas 














5. Lignite ..... 


22.95 


23.64 


43.31 


5.10 




1.51 


S. Platte field, Col. 














6. Lignite 


21.11 


28.55 


44.98 


5.01 




1.58 


E. field, Montana 















COAL 



Locality 


Moisture 


Volatile 
Hydro- 
carbon 


Fixed 
Carbon 


Ash 


Sulph. 


Fuel 
Ratio 


7. Lignite 


10.80 


43.10 


38.57 


7.53 




.87 


Corral Hollow, Cal. 














8. Brookville Coal . . 


1.47 


17.93 


75.508 


4.525 


.567 


4.21 


Conemaugh, Cam- 














bric Co. 














9. Pittsburg Coal . . . 


1.26 


31.79 


57.79 


7.16 


.79 


1.81 


Connelsville, Fay- 














ette Co. 














10. Hocking Valley Coal 


5.93 


36.48 


52.41 


5.13 


1.09 


1.44 


Ohio 














11. Warrior 


4.83 


18.95 


72.76 


3.28 


.17 


3.83 


Jeff. Co., Ala. 














12. Jellico 


4.40 


31.56 


61.87 


1.86 


.31 


1.96 


Campbell Co., Tenn. 














13. Brazil Block Coal . 


13.82 


35.16 


49.96 


1.06 


1.47 


1.42 


Brazil, Ind. 














14. Cannel Coal . . . 


1.47 


49.08 


26.35 


23.10 


1.48 


.53 


Cannelburg, Ind. 














15. Bituminous Coal . . 


5.50 


39.50 


54.60 


5.40 


. . . 


1.38 


Belleville, 111. 














16. Butler 




30.66 


54.94 


11.00 


2.544 


1.71 


Kentucky 














17. Owasso Coal Comp'ny 


7.58 


35.70 


52.96 


3.76 


1.50 


1.48 


Owasso, Mich. 














18. Saginaw Company . 


5.82 


39.79 


45.15 


9.24 


3.83 


1.13 


Verne, Mich. 














19. Fort Dodge . . . 


7.48 


39.52 


45.54 


8.44 


5.28 


1.15 


Iowa 














20. Lexington .... 


9.24 


29.01 


42.19 


15.18 


4.38 


1.45 


Missouri 














21. Hartshorne Coal . . 


1.68 


41.00 


51.91 


5.41 


2.72 


1.26 


Hartshorne, I.T. 














22. Gwyn's shaft . . . 


.892 


14.57 


77.09 


6.24 


1.19 


5.28 


Sebastian Co., Ark. 














23. Semi-bituminous . . 


1.10 


11.27 


72.83 


12.04 


2.74 


6.46 


Johnson Co., Ark. 














24. Coal No. 1 . . . . 


.88 


31.57 


56.81 


8.93 


1.47 


1.79 


Thurber, Texas 














25. Coking Coal . . . 


.75 


31.13 


57.07 


11.05 


. . . 


1.80 


Raton field, Col. 















ECONOMIC GEOLOGY OF THE UNITED STATES 



Locality 


Moisture 


Volatile 
Hydro- 
carbon 


Fixed 
Carbon 


Ash 


Sulph. 


Fuel 
Katio 


26. Newcastle .... 


7.992 


29.031 


53.806 


8.023 


1.148 


1.85 


Washington 














27. Bituminous Coal . . 


6.21 


31.32 


52.47 


11.10 


. • . 


1.65 


Canyon City, Col. 
28. Anthracite .... 


1.58 


6.70 


87.46 


4.26 


.58 


13.05 


Crested Butte, Col. 














29. Anthracite .... 


2.90 


3.18 


88.91 


5.21 


. . . 


27.96 


Cerillos field, New 














Mexico 














30. Mammoth .... 
W. Middle field, Pa. 


3.163 


3.717 


81.143 


11.078 


.899 


21.83 


31. Mammoth .... 
N. Middle field, Pa. 


3.421 


4.381 


83.268 


8.203 


.727 


19.00 



The moisture can be driven off at 100° C. and is usually highest in 
peat and lignite ; the volatile hydrocarbons are the easily combustible 
elements, and decrease toward the anthracitic end of the series; the 
fixed carbon burns with difficulty and is highest in the anthracite 
coals. The ash represents noncombustible mineral matter and bears 
no direct relation to the kind of coal ; and the same is true of sulphur, 
which is present as an ingredient of pyrite or gypsum. 

The value of coal for fuel or other purposes is determined mainly 
by the relative amounts of its fuel constituents, viz. the volatile hydro- 
carbons and the nonvolatile or fixed carbons. The fuel value, or fuel 
ratio, is determined by dividing the fixed carbon percentage by that 
of the volatile hydrocarbons. 

The fixed carbon represents the heating element of the coal, while 
the volatile hydrocarbons burn easily, but have little heating power. 
The heating power and fuel ratio will, therefore, increase together. 
This increase in the heating power of the coal is only true, however, 
up to a certain point, after which the difficulty in making the coal 
burn offsets the extra amount of heat developed. Coals with a high 
percentage of fixed carbon develop great heating power, while those 
lower in fixed carbon and high in volatile hydrocarbons lack in heating 
power, but are free burning. 



COAL 



9 



Moisture is a nonessential constituent of coal. It not only dis- 
places so much combustible matter, but requires heat for its evapo- 
ration. When present in large amounts it often causes the coal to 
disintegrate while drying out. It ranges from 1 per cent in anthracite 
to 20 or 30 per cent in lignites. 

Ash also displaces combustible matter, but otherwise it is in most 
cases an inert impurity. The clinkering of coal is commonly due to 
a high percentage of fusible impurities in the ash, and for metallur- 
gical work the composition of the ash often has to be considered. 

The following analyses will also serve to illustrate the composition 

of the ash: — 

Ash Analyses 



Peat, average of 

several . . . 

Lignite . . . . 

Bituminous Coal 



Si0 2 


Al 2 O s 


Fe 2 3 


CaO 


MgO 


MnO, 


so 3 


Alka- 
lies 


Chlo-I 
rine 


25.50 


5.78 


18.70 


24.00 


3.20 




7.50 


1.72 


.60 


30.14 


13.48 


11.70 


23.59 


.88 


3.32 


14.22 






34.32 


14.62 


22.94 


14.85 


1.42 


1.16 


10.97 







p»o a 



2.56 



Sulphur is an objectionable impurity in steaming coals on account 
of its corrosive action on the boiler tubes. It is also undesirable in 
coals to be used for metallurgical purposes and gas manufacture. 

Origin of Coal W. — It has been shown that there are 
gradations between unquestioned plant beds and mineral 
coal, and that coal, besides containing the same materials 
as plant tissue, often shows the presence of plant fibers, 
leaves, stems, seeds, etc. Moreover, stumps or trunks of 
trees are sometimes found standing upright in the coal, 
with their roots penetrating the underlying bed of clay (5), 
just as trunks of trees at present stand in bogs. While 
these facts point unmistakably to a vegetable origin of 
coal, it is less easy to understand the exact manner in 
which the great accumulations of vegetable matter have 
been made, and the changes from plant tissue to mineral 



10 ECONOMIC GEOLOGY OF THE UNITED STATES 

coal. Each of these points, therefore, demands further 
consideration. 

Conditions of Vegetable Accumulation (4). — At present 
there are several conditions under which plant remains 
accumulate to considerable depth over areas in some cases 
of large size. All of these are closely associated with 
water, either fresh or salt, because plant remains falling 
in water have their decay so retarded by the exclusion of 
air that accumulation is possible. Of these the following 
are the most important : (1) accumulation due to algae on 
the sea bottom beneath a sargasso sea ; (2) marine swamps, 
including salt marshes and mangrove swamps ; (3) delta 
deposits; (4) peat bogs; (5) coastal plain marshes. 

While accumulations made in any one of these ways 
may form coal beds, and while individual beds may be 
formed which are due to any of these causes, to many of 
them there are such objections as to render them extremely 
improbable as general explanations for the great number 
of widely extended deposits of coal. The theory of accumu- 
lation from deposits of algae, for example, demands deep 
water of an open ocean for the circulation of ocean cur- 
rents.. But most coal beds are evidently formed either on 
the land or else in shallow water of lakes, lagoons, or sea- 
coast swamps. 

To the theory of various swamps there are two serious 
objections : (1) that in such deposits as are now forming, 
the currents are bringing more fragmental sediments than 
are commonly present in coal beds ; (2) that at present 
only one kind of tree, the mangrove, is adapted to growth in 
salt water. It is, of course, possible that in earlier ages the 
number of trees adapted to this mode of life was far greater. 



COAL 11 

Streams are bringing plant remains to lakes or oceans 
and incorporating them in their deltas ; but nowhere are 
such, extensive accumulations now forming as to make large 
coal fields in this manner. Moreover, the amount of sedi- 
ment brought in such places would seem to exclude the 
possibility of the deposit of large areas of vegetable mat- 
ter free from a great admixture of sediment. The combi- 
nation of this source of vegetable supply with that caused 
by the growth of marine or fresh-water swamp plants in 
the delta lagoons would increase the chances of the forma- 
tion of coal beds by this means; but even with this addi- 
tion, it seems impossible to accept this as a general theory 
for the formation of extensive beds of coal. 

It is a well-known fact that thick deposits of vegetable 
matter, often covering areas of several square miles, are 
formed in the peat bogs that in so many places represent 
the last stage of lake or pond filling in cool, temperate 
climates. Each of these bogs would, under favorable 
circumstances, change to a bed of coal, and some of them 
are extensive enough to form coal beds of large size. But 
such bogs are, compared to our larger coal fields, far too 
limited in area to admit of the acceptance of this explana- 
tion to account for great coal fields without assuming far 
more widespread bog-forming conditions than any at present 
known. 

Perhaps the most perfect resemblance to coal-forming 
condition is that now found on such coastal plain areas as 
that of southern Florida and the Dismal Swamp of Virginia, 
North Carolina. Both of these areas are very level, though 
with slight depressions in which there is either standing 
water or swamp conditions. In both regions there is such 



12 ECONOMIC GEOLOGY OF THE UNITED STATES 

general interference with free drainage that there are exten- 
sive areas of swamp, and in both there are beds of vegetable 
accumulations. In each of these areas there is a general 
absence of sediment and therefore a marked variety of vege- 
table deposit. If either of these areas were submerged be- 
neath the sea, the vegetable remains would be buried and a 
further step made toward the formation of a coal bed. Re- 
elevation, making a coastal plain, would permit the accumula- 
tion of another coal bed above the first, and this process 
might be continued again and again. 

In support of the theory that coal was accumulated in 
some such situation as this, are a number of facts : (1) the 
coal beds occur over wide areas in sediments which were 
deposited near land borders and which may therefore have 
been again and again raised above sea level to form extensive 
coastal plains ; (2) there are evidences of land conditions re- 
vealed in the workings of some mines ; (3) the enormous 
area of some coal fields call for some such widespread condi- 
tions as coastal plains might provide ; (4) the slight admix- 
ture of sediment indicates the absence of conditions of 
sediment supply, e.g. rivers, waves, tidal currents, and wind- 
formed currents ; (5) vegetable accumulations made in such 
situations would require but slight changes in land level to 
be buried beneath sedimentary strata as the coal beds have 
been. 

Chemical Changes occurring during Coal Formation. — 
Dead plant tissue when exposed to the air oxidizes rapidly 
and decays, all of the gaseous elements passing off, leaving 
only the mineral matter which the plant tissue contained. 
The exclusion of air caused by the presence of water, as in a 
pond or a swamp, greatly retards oxidation ; but, as it slowly 



COAL 



13 



proceeds the oxygen, nitrogen, and hydrogen of the plant 
tissue, together with some of the carbon pass off in the form 
of carbon dioxide (C0 2 ), carbon monoxide (CO), marsh gas 
(CH 4 ), and water. As a result, as the process continues 
an increasing percentage of carbon is left behind. The 
change is also accompanied by a change in color to deep 
brown, and finally to black. 

The changes that take place in the passage of vegetable 
matter into coal are graphically shown in the following dia- 
gram prepared by the late Professor Newberry : — 



VEGETABLE TISSUE PEAT 



'ITUM. CVL ANTHRACITE GRAPHITE 



B 












H.O.N, 




G 


EVOLVED 


GASES 






F 


VOLATILE 
fcJYDROCAR 
l~~~^-~— -_ . 


co 2 . C 

30NS^\^ 


0, H 2 0, CH 
J 


, ETC 




C 


FIXED 


CARBON 




M 


K 

>T~~ — 


MINERAL 


MATTER 


OR 


ASH 







Fig. 1. — Diagram showing changes occurring in passage of vegetable 
tissue to graphite. After Newberry. 

In this diagram the rectangle ABCD represents a given 
volume of fresh vegetable matter, which contains a small 
percentage of mineral matter, the rest being organic sub- 
stances consisting roughly of 50 per cent carbon (EFCD) 
and 50 per cent hydrogen, oxygen, and nitrogen (ABEF). 
In the change from fresh vegetable tissue to peat, part of 
these four elements pass off as gaseous compounds, so that 
the remaining volume of peat is less (BGDH) than the origi- 
nal volume of vegetable matter (ABCD). Since, however, 
H, O, and N have passed off in larger amounts than the 
carbon, the percentage of the latter in the peat will be higher 
than it was in the fresh plant tissue. (Compare BFGI and 



14 



ECONOMIC GEOLOGY OF THE UNITED STATES 



FIDH with ABEF and EFCD.) The actual weight of 
mineral matter will be the same, but its percentage will be 
larger. This change continued will result finally in anthra- 
cite, the last of the coal series, in which the per cent of carbon 
(LKMN) is high and that of the other organic elements low 
(JKL). The amount of compression that occurs in such 
changes as those illustrated in the diagram may be under- 
stood when it is stated that it is estimated that from 16 to 
30 feet of peat are required to make one foot of true coal. 

The following analyses of various grades of coal from peat 
to anthracite clearly illustrate this gradual concentration of 
carbon by loss of volatile elements. 

Elementary Analyses of Coals 








c. 


H. 


0. 


N. 


s. 


Ash 


Mois- 
ture 


Peat 


59.47 


6.52 


31.51 


2.51 






22 


Lignite 

Bituminous coal 


58.44 
68.13 


4.97 
6.49 


16.42 
5.83 


1.30 

2.27 


2.48 


12.30 




Breckenridge Co., Ky. 
Bituminous coal 


73.80 


5.79 


16.58 


1.52 


.41 


1.90 




Ohio 
















Bituminous coal 


82.70 


4.77 


9.39 


1.62 


.45 


1.07 




Clay Co., Ind. 
Anthracite ...... 


90.45 


2.43 


2.45 






4.67 




East Pa. 

















Effect of Heat and Pressure. — While the first stage in 
coal formation is brought about simply by the exclusion of 
air, for further development pressure seems necessary. 
Even in peat beds the lower layers are under the gentle 
pressure of the upper layers; but peat is not changed even 
to lignite until buried under many feet of sediments. Great 
pressure, possibly aided by heat, seems necessary for the 



COAL 15 

change from lignite to bituminous coal ; and long periods of 
time are apparently required for the slow changes to take 
place. That heat may sometimes have been present is indi- 
cated by the evidence of rock folding that is sometimes, 
though by no means invariably, present in bituminous coal 
areas. 

Most of the anthracite coal in the United States occurs in 
the highly folded Appalachians of Pennsylvania. Such fold- 
ing must have been productive of much heat and pressure, 
and that the folding has produced the anthracite is by many 
believed to be proved by the fact that these coal beds pass 
into bituminous coal when traced southward or westward 
into areas of less disturbances. This view is questioned by 
some geologists, especially J. J. Stevenson, who has argued 
that the anthracite has not been developed from bituminous 
coal by metamorphism, but that the volatile constituents 
were partly removed by longer exposure of the vegetable 
matter to oxidation before burial (7). 

There are some cases, as in the Cerillos coal field of New 
Mexico (50), where anthracite probably has been produced 
by heat. Here a bituminous coal has been deprived of its 
volatile matter and converted into anthracite in those por- 
tions of the bed near an intrusion of andesite. A similar 
change has taken place in the Crested Butte district of 
Colorado (29). 

Structural Features of Coal Beds. — Outcrops (13).— The 
outcrop of a coal bed is usually easily recognizable on 
account of its color and coaly character; but unless the 
exposure is a rather fresh one, the material is disintegrated 
and mellowed, the wash from it mingling with the soil, and 



16 



ECONOMIC GEOLOGY OF THE UNITED STATES 



if the outcropping bed is on a hillside, often extending some 
feet down the slope. This weathered outcrop has been 
termed the " smut " or "blossom " by coal miners. In 
areas where the beds have been tilted and the slopes are 
steep, the outcrops of coal can usually be 
easily traced ; but in regions where the dip 
is low and the surface level, the search for 
coal is often attended with difficulty, which 
is increased if the country is covered with 
glacial drift. In such cases boring or pit- 
ting is commonly resorted to. 

Associated Bocks. — Most coal beds are 
interbedded with shales, clays, or sand- 
stones, though conglomerates or limestones 
are at times also found in close proximity. 
Coal beds are often underlain by a bed of 
clay, which in some regions is of refractory 
character (Fig. 2); but the widespread 
belief that all these under clays are fire 
clays is unwarranted. 

Variations in Thickness. — Coal beds or 
are rarely of uniform thickness 





"•'•'] 


Coal 


H 


Fire Clay 






-_== 




^L. 


Coal 


: | 


Coal 
Fire Clay 


23 


Coal 


HB 



seams 



Fig. 2. — Section in 
coal measures of 
western Pennsylva- 
nia, showing fire over large areas; indeed, a bed which is 

clay under coal ? m • , , i • i , i 

beds. After Hop- °* sufficient thickness to work in one mine 
kms ' may be so thin in a neighboring mine as 

to be scarcely noticeable. This irregularity is in some cases 
due to variations in thickness of vegetable accumulations, 
in other cases to local squeezing of the coal bed subsequent 
to its formation. These thinnings and thickenings are com- 
monly called "pinchings" and "swellings" (Fig. 3). In 
regions of pronounced folding, the coal beds are usually 



COAL 



17 



found in separate synclinal basins, the intervening anticlinal 
folds having been worn away. 

Other Irregularities. — Splitting (Fig. 3) is a common 
feature of many coal seams. The Mammoth bed, so promi- 
nent in most of the anthracite basins of Pennsylvania, splits 







__ < ^_ != . -=L__=^= 


- _a 


-^==S=?- =^=^^^=^^5, 




i^pgs^l 


= = " ' 


^y^s^^T 


- 


= 3*i=?°:£~<F ~ 




^PIP 




™ 


S^S^S 


m 


■^Sgf^lB 



Fig. 3. — Section showing irregularities in coal seam, a, split; 
6, parting of shale; c, pinch; e?. swell; e, cut out. 

into three separate beds in the Wilkesbarre basin. This 
splitting is caused by the appearance of beds of shale (called 
" slate " by coal miners), which often become so thick as 
to split up the coal seam into two or more beds. When 
narrow, such a bed of slate is called a parting. The Pitts- 
burg seam of western Pennsylvania shows a fire-clay parting 
or " horseback" (Fig. 3) 
from six to ten inches 
thick over many square 
miles. 

In addition to these 
u slate " partings, which 
run parallel with the bed- 
ding, others are often 
encountered which cut 
across the beds from top 
to bottom. These in some cases represent erosion channels, 
formed in the coal during or subsequent to its formation, 
and later filled by the deposition of sand or clay. In other 




Fig. 4. — Section of faulted coal seam. 
After Eeyes, la. Geol. Surv., II: 86, 1894. 



18 ECONOMIC GEOLOGY OF THE UNITED STATES 

cases they are due to the filling of fissures formed during 
the folding of the strata. 

Faulting (Fig. 4) is not an uncommon feature of coal 
beds, and the coal is sometimes badly crushed on either side 
of the line of fracture. The amount of throw and the num- 
ber and kind of faults may vary, so that one might expect 
normal, reverse, overthrust, and even step faults. 

Coal Fields of the United States (PI. I). — Coal in com- 
mercial quantities occurs in twenty-seven of the forty-seven 
states and territories as well as in Alaska. These occur- 
rences can be grouped into nine well-marked fields, as 
follows : — 

(1) Appalachian, including parts of Pennsylvania, Ohio, 

Maryland, Virginia, West Virginia, Eastern Ken- 
tucky, Tennessee, Georgia, and Alabama . . 71,291 sq. mi. 

(2) Rhode Island Very small. 

(3) Atlantic Coast Triassic, including parts of Virginia 

and North Carolina 1070 sq. mi. 

(4) Eastern Interior, including parts of Indiana, Illinois, 

and western Kentucky 58,000 sq. mi. 

(5) Northern Interior, including parts of Michigan . 11,300 sq. mi. 

(6) Western Interior, including parts of Iowa, Missouri, 

Nebraska, and Kansas 66,200 sq. mi. 

(7) Southwestern field, including parts of Indian Terri- 

tory, Arkansas, and Texas . .... 27,876 sq. mi. 

(8) Rocky Mountain field, including parts of South Da- 

kota, Montana, Idaho, Wyoming, Utah, Colorado, 

and New Mexico 43,610 sq. mi. 

(9) Pacific Coast, including parts of Washington, Oregon, 

and California 1050 sq. mi. 

The above grouping does not include the areas of lignite- 
bearing formations, although these are shown on the map 



COAL 19 

(PL I). According to Hayes there are in Montana, the 
Dakotas, and Wyoming, approximately 56,500 square miles 
of lignite-bearing formations, chiefly of Cretaceous age. 
A series of fields in the Tertiary of Alabama, Mississippi, 
Louisiana, Arkansas, and Texas cover approximately as 
large an area. 

The estimates given above are of course only approximate, and some 
of these fields may be extended in the future by the development of 
areas now classed as unproductive. This applies especially to those in 
which the coal lies too deep to be profitably mined at present. It is a 
noteworthy fact that the production of the fields is by no means propor- 
tional to their areas. (Compare above list with table, p. 34.) Proximity 
to markets, value of the coal for fuel, and relative quantity of coal per 
square mile of productive area, are factors of importance in determining 
the output of a field. 

Geologic Distribution of Coals in the United States. — The 
coal-bearing formations of the United States range in age 
from Carboniferous to Tertiary. Carboniferous coals occur 
east of the 100th meridian, Cretaceous coals between the 
100th and 115th meridian, and the Tertiary coals chiefly 
between the 120th meridian and the Pacific coast. Excep- 
tions to this distribution are the occurrence of a small area 
of Triassic coals in Virginia and North Carolina, and a large 
Tertiary area of lignite in the Gulf States. This indicates 
that during the coal-forming periods there was in North 
America a slow westward shifting of the zone in which 
conditions favorable to coal formation occurred, the only 
exceptions being those mentioned above. 

The Carboniferous coals are commonly grouped into 
several well-marked and clearly separated areas; but this 
isolation is probably the result of folding and erosion, all 



20 



ECONOMIC GEOLOGY OF THE UNITED STATES 



excepting the Michigan field having apparently been origi- 
nally continuous. To a certain extent the same is true 
=j <3 of the Rocky Mountain coal fields. 

-I rg 

zs g These have often been seriously dis- 

turbed by post-Cretaceous uplifts, 
which in many instances have im- 
proved the qualities of the coal. As 
a whole, the Tertiary coals are medium 
to low grade, though in some sections, 
notably in Washington, they are of 
excellent quality. 






§2 



fcJD *. 

OS o 

S3 



bJO^ 



Appalachian Field (12, 15, 18, 55, 58, 
60, etc.). — This, the most important 
coal field in the United States, ex- 
tends 850 miles, from northeastern 
Pennsylvania to Alabama, and about 
75 per cent of its area contains work- 
able coal. At the southern end the 
coal measures pass beneath the coastal 
plain deposits, and they may connect 
with the Arkansas coal measures be- 
neath the Mississippi embayment. 

Being closely associated with the 
Appalachian Mountain uplift, the coal 
measures of this region partake of the 
structural features of the Appalachian 
belt. Thus, while the strata of the 
western portion are either horizontal 
or only slightly bent, those farther 
east are often highly folded (Fig. 7), and in the southern 



< § 



CD -~ 

O c3 



COAL 21 

Appalachians the strata are both folded and faulted (Fig. 5). 
Extensive erosion following the folding of the coal meas- 
ures has resulted in the development of a number of 
basins. 

The coal measures of the Appalachian field consist of a 
great thickness of overlapping lenses of conglomerate, sand- 
stone, shale, coal, and some limestones, and owing to this 
lenticular character of the deposits, and to local thickenings, 
it is difficult to trace individual beds of coal over wide areas, 
or to correlate sections at widely separated points. 

The middle Carboniferous, or Pennsylvanian, includes 
most of the coal beds of the Appalachian area, and is 
divided into the following five major subdivisions which are 
recognizable throughout the field : (1) Dunkard or Upper 
Barren Measures; (2) Monongahela or Upper Productive 
Measures ; (3) Conemaugh or Lower Barren Measures ; 
(4) Alleghany or Lower Productive Measures ; (5) Pottsville 
or Serai Conglomerate. 

This classic section was first worked out in Pennsylvania, 
and has since been identified in other parts of the Appa- 
lachian field. At the time it was made, the second and 
fourth members were thought to be the only ones carrying 
coal, and hence the name " Productive " ; but since then the 
Pottsville has been found to be locally productive, and a few 
seams have been found even in the Barren Measures. 

The Appalachian field is divisible into two parts of very 
unequal size : (1) the anthracite field of northeastern 
Pennsylvania ; and (2) the bituminous area, which occu- 
pies the balance of the field. 

Bituminous Area (15, 20). — In western Pennsylvania, where 
we have the type section of the Carboniferous of eastern 



22 ECONOMIC GEOLOGY OF THE UNITED STATES 

America, about 95 per cent of the coal mined comes from 
the Alleghany and Monongahela groups, though beds of 
coal are found as high as the Dunkard and as low as the 
Potts ville. While most of the coal beds are of limited 
extent, the celebrated Pittsburg bed, at the base of the 
Monongahela, has an average thickness of 6 feet over an 
area of 50 miles square. Its original capacity, estimated to 
be 10,000,000 tons of available coal, makes it one of the 
most important bituminous coal beds in the world. This 
same bed is recognizable and important in Ohio and Mary- 
land. 

In the southern portion of the Appalachian held, the coal 
beds lie in the Pottsville, which here is much thicker than 
farther north, reaching a maximum thickness of 5000 to 6000 
feet, as against 300 feet in western Pennsylvania, and most 
of the workable coal occurs in its upper portion. 

Character of Appalachian Bituminous Coals. — The coals of this field 
differ greatly from place to place. In general there is a decrease in 
volatile hydrocarbons from the west toward the east and southeast. 
Good coking coals are found throughout the field. Those of Maryland 
are semi-bituminous, and have a high reputation for steaming purposes ; 
but those of Pennsylvania include many coking coals, and are hence of 
farther value in smithing, and coke and gas manufacture. While much 
of the coke is used locally by the great metallurgical establish- 
ments, a large amount is also shipped to other states, even in the 
far Northwest. 

The markets for these coals are chiefly in the South where, excepting 
along the seacoast, they come into successful competition with the Penn- 
sylvania anthracite for domestic purposes. In the north and northwest 
they compete less successfully with coals from the interior fields. 

Pennsylvania Anthracite Field (18) . — This field (Fig. 6) 
lies in the eastern central part of the state, covering an area 



COAL 



23 



of about 3300 square miles, about one-seventh of which 
is underlain by workable coal measures. Intense folding 
(Fig., 7) has placed some of the coal in the synclinal troughs 
where it has been preserved from erosion which has removed 
the coal from the intervening anticlines. Therefore the 
anthracite is found in a 
number of more or less 
separated narrow basins. 
It has been estimated that 
from 94 to 98 per cent of 
the coal originally depos- 
ited has been removed from 
this field by denudation. 

The coal measures of the 
anthracite district consist 
of beds of sandstone, shale, 
and clay, with coal beds at 
intervals varying from a 
few feet to several hundred 
feet, though rarely exceed- 
ing 200 feet. The coal 
beds, which vary in thick- 
ness from a few inches to 50 or 60 feet, occur through- 
out the entire section of the coal measures, but are most 
important in the lower 300 to 500 feet. Beneath the Pro- 
ductive Measures is the hard Pottsville conglomerate, 
which forms an important stratigraphic horizon, recogniz- 
able by its lithological character and bold outcrops. Local 
variations in the coal beds, and lack of uniformity in naming 
them, have rendered their correlation in the different fields 
more or less difficult. 




Fig. 6. — Map of Pennsylvania anthracite 
field. After Stoek, U. S. Geol. Surv., 
22dAnn. Rept., Ill . 



24 



ECONOMIC GEOLOGY OF THE UNITED STATES 



The position of the coal beds and physical characteristics of the coal 
have necessitated the use of special methods of mining and of treat- 
ment after mining. Sharpness of folding and steep dips prevail, these 
introducing many mining problems not found in bituminous regions. 
When brought to the surface, it consists of lumps varying in size and 
mixed with more or less shaly coal, called "bone," so that, before ship- 
ment to market, it is necessary to break, size, and sort it. This is done 




Section (C)across the Panther Creek Basin 



F IG . 7 . _ Sections in Pennsylvania anthracite field. After Stoek, U. S. Geol. 
Surv., 22d Ann. Sept., Ill: 72. 



in a coal breaker (Fig. 8), in which the coal is crushed in rolls, and sized 
by screens, while the slate is separated either by hand, automatic pickers, 
or jigs. These breakers are a prominent feature of the anthracite region, 
and much money has been spent in increasing their efficiency. As the 
result of years of mining, the refuse from the breakers, consisting of a 
fine coal-dust and bone, termed " culm," has accumulated in enormous 
piles. Much of it is now being washed to save the finer particles of 
clean coal ; and much is also washed into the mines to support the roof, 
so that the pillars of coal, originally left for that purpose, can be 
extracted. 



COAL 



25 



On account of its cleanliness and high fuel ratio, anthra- 
cite coal is much prized for domestic purposes. Most of that 
mined is marketed in the* eastern and middle states, although 
small quantities are shipped to the western states, especially 
those that can be reached by way of the Great Lakes. 




Fig. 8. — Coal breaker in Pennsylvania anthracite region. 

Rhode Island Field (63, <>i). — A small area of metamorphosed, folded, 
and faulted Carboniferous occurs in the Narragansett Bay region of 
Rhode Island, extending up into Massachusetts. The inclosing strata 
of conglomerate and clay are often changed to schist, and the coal to a 
form of anthracite so nearly pure carbon as to be exceedingly difficult 
to burn. In fact, in places the coal has been metamorphosed to graphite. 
Attempts to utilize this have not met with much success on account of 
the high percentage of impurities which the material contains. 

The Triassic Field (52). — This coal field which is more important 
historically than economically, having been worked as early as 1700, 
includes several small steep-sided basins lying in the Piedmont region of 
Virginia and Xorth Carolina. It is probable that the coal-bearing beds 
of the several areas, originally horizontal, were formerly continuous, 
having been separated by folding, faulting, and denudation. In addition 
to this, the coal is cut by dikes and sheets of igneous rock, which have 
locally altered it to natural coke or carbonite. 



26 



ECONOMIC GEOLOGY OF THE UNITED STATES 



\\ 



Eastern Interior Field (13, 32). — This 
field is an oval, elongated basin (Fig. 
9) extending northeast and southwest, 
with the marginal beds dipping gently 
toward the lowest portion, which lies 
in Illinois, where the beds are nearly 
horizontal. 

The coal-bearing rocks rest uncom- 
formably on lower Carboniferous, Devo- 
nian, and Silurian strata, the basal 
member being a sandstone probably the 
equivalent of the Pottsville. The 
entire section of coal-bearing rocks, 
attaining a thickness of 1200 feet, 
belongs to the Coal Measures, although 
the upper part may be of Permian age, 
and the highest workable coal beds are 
classed as Freeport or Conemaugh. 
The coal seams occur in the lower 
portion of the section, and hence out- 
crop around the margin, and the mining 
operations are confined to a narrow belt, 
because near the center of the basin the 
coal beds underlie too great a thick- 
ness of unproductive strata to permit 
of profitable working under present 
conditions. 

Great difficulty has been encountered 
in attempts at correlation of the coal 
beds of different parts of the field, be- 
cause of the varying section shown 



COAL 



27 



from place to place, and lack of continuity of the beds. 
In consequence, the custom has arisen of giving the coal 
beds numbers instead of names. 

In Indiana coal is found in at least twenty horizons with workable beds 
in not less than eight ; but at any given point the number of workable 
beds never exceeds three, and in places there is only one. One of the 
Indiana coals is known as "block coal," the name arising from the fact 
that the presence 
of joint planes at 
right angles causes 
the coal to break 
into blocks. 

There are many 
coal beds in Illinois 
worked at depths 
of from 50 to 200 
feet or more; but 
there is a marked 




Fig. 10. 



Shaft house and tipple, bituminous coal mine, 
Spring Valley, 111. 



absence of stratigraphic knowledge regarding this part of the field. 
In Kentucky, on the other hand, there are only two workable coal beds 
of decided importance, and fully 75 per cent of the coal produced in the 
strata comes from the upper of these. This bed is so persistent that it 
underlies a part of the whole of 8 counties, with an average thickness of 
5 feet and at a depth commonly less than 200 feet. 

The coals of the eastern interior field, although varying widely in 
quality, are all bituminous. On account of their higher percentage of 
ash and sulphur, they are little used for coking. Most of the coal used 
in and near this field is supplied from it ; but even within the field the 
Appalachian coals enter into competition. The Cannel coal found near 
Cannelsburg, Kentucky, which is the only good gas producer found in 
this field, finds a ready market. 

Northern Interior Field (43). — This field forms a large 
basin in which the coal dips irregularly from the margin 
toward the center (Fig. 11), but on account of the heavy 



28 



ECONOMIC GEOLOGY OF THE UNITED STATES 



mantle of glacial drift it has been difficult to determine 
its exact boundaries, and prospecting is necessarily done 
by means of drilling. The coal measures attain a total 
thickness of 600 to 700 feet in the center of the basin, and 
include 7 horizons of workable coal with an average 
thickness of 2 feet and rarely exceeding 4 feet. Coal 
is found near the center of the basin at depths of 400 
feet or more, though the beds that are mined are mostly 




Horizontal scale 



Vertical scale 



Fig. 11. — Generalized section of Northern Interior coal field. After Lane, 
U. S. Geol. Surv., 22d Ann. Rept., Ill: 316. 

at depths of 100 to 150 feet. All the coals are bituminous 
and used chiefly for fuel, but some are coking, and others 
will probably prove of value for gas manufacture. 



Western Interior Field and Southwestern Fields (14). — 
These two fields form a practically continuous belt of coal- 
bearing formations, extending from northern Iowa south- 
westward for a distance of 880 miles into central Texas. 
Throughout most of this area the beds lie horizontal, or 
have a gentle westward dip averaging 10 to 20 feet per mile. 
A notable exception is found in the beds of eastern Indian 
Territory and Arkansas which are rather strongly folded, 
reminding one of the Pennsylvania anthracite area. 



COAL 



29 



Western Interior Field. — The coal measures, composed of 
limestones, sandstones, shales, fireclays, and coal beds, rest 
unconformably on the Mississippian and dip westwardly 
under beds of Permian, Cretaceous, and Pleistocene (Fig. 12). 
Toward the south and west the beds increase in thickness, 
the maximum being 1000 feet in Iowa (36) and 3000 in 
Kansas (37). 

Most of the coal mined in this field comes from the lower 
part of the coal measures where the beds are irregular in 




Fig. 12. — Composite section showing structure of lower coal measures of Iowa. 
After Keyes, la. Geol. Surv., I: 105. 

thickness and distribution, in consequence of deposition on 
a very uneven surface. 

All the coals of this field are essentially bituminous and used chiefly 
for steaming and heating purposes, being of no value for either coking 
or gas making. Some of the seams will coke, but there is no demand for 
the product, and the sulphur and ash are too high for gas making. 

Southwestern Field. — While it is known that there is 
much good coal in this field, full development has not been 
undertaken in most parts of it. The Indian Territory 
coals (34, 35), of which there are 7 important beds in a 
section of 4500 feet of shales and sandstone, are both folded 
and faulted. These coals, as well as those of Texas (69), 
where there are three workable beds, are all bituminous; 



30 ECONOMIC GEOLOGY OF THE UNITED STATES 

but in the eastern end of the Arkansas (25) field there is 
anthracitic coal of probable Permian age. 

The coal from this field finds its most important market 
in the South, though some is sent North. The Texas coals 
are of especial importance on the railways, being used as 
far west as the Pacific coast. It has, however, found a 
serious competitor in the Texas crude petroleum ; but it 
remains to be seen whether this competition will be lasting. 
On account of the value for domestic purposes the anthra- 
cite finds an important market to the northward. 

Gulf States Lignite Area (9). — There is a narrow lignite- 
bearing belt extending across the lower part of Alabama 
and Mississippi; and another much larger belt extending 
from near Little Rock, Arkansas, southwestward across the 
northwestern corner of Louisiana (42), and in a narrowing 
belt across Texas. Both of these are of Eocene age. The 
lignites are usually high in moisture and ash, the best grade 
being that mined in the lower end of the area, near Laredo 
on the Rio Grande. 

A small field of Cretaceous lignitic coal has been devel- 
oped around Eagle Pass on the Rio Grande (70). This 
is an extension of the Mexican field, but is of poorer 
quality. 

Rocky Mountain Fields (17). — These cover a broad area, 
extending from the Canadian boundary southward into 
New Mexico, a distance of about 1000 miles, and includ- 
ing over 50 fields of various size and irregular shape. 
Most of the beds lie within the mountainous region, but at 
the northern end of the area, in Wyoming and the Dakotas, 
the coal fields extend eastward under the plains for some 



Plate II 




Fig. 1. — Pit working (S trippings) near Milnesville, Pa. The Mammoth seam is 
uncovered in hottom of pit. 




Fig. 2. — Lignite seam, Williston, N.D. After Bub cock photo. 



COAL 31 

distance. The age of the coal ranges from Cretaceous to 
Tertiary, though most of it belongs to the former. 

While portions of this enormous area of coal-bearing 
strata are only slightly disturbed, mountain-building forces 
and igneous intrusions have affected a large proportion of 
the region, often materially changing the character of the 
coal. Thus, while in undisturbed portions of the field the 
beds are lignitic (PI. II, Fig. 2), in the disturbed parts they 
have been altered to bituminous and even to anthracite 
coal. Some of the bituminous coals produce an excellent 
quality of coke. 

Colorado (29, 30) is the most important coal -producing state of the 
Rocky Mountain region. This is due, not only to the quality of its 
coals, but also to the presence within the state of extensive metal- 
lurgical industries. The Raton field, in the southeastern part of the 
state and extending into New Mexico (50, 51), is at present the most 
important producer. Like many of the fields of this region the age 
of these is Laramie, and the beds are both folded and faulted. They 
are, moreover, crossed by igneous intrusions which have in some places 
produced natural coke, but in others destroyed the value of the coal. 
In a section of from 3000 to 4500 feet of Laramie strata there are 40 
coal beds, only a few of which are, however, workable. There are 
both coking and semi-coking coals, and some anthracite. 

In Montana (45, 46, 47) the coals range in age from Triassic to Ter- 
tiary, and in quality from lignite to bituminous. The coals of Wyoming, 
which occupy a very large area, show the same range in quality, but 
are more commonly lignite because found to so large an extent in re- 
gions of slight disturbance. The Utah coals are prevailingly semi- 
bituminous, and those of the two Dakotas lignitic. 

The Pacific Coast Fields (16). — Tertiary coals, partly 
bituminous, though mainly lignitic, occur scattered over a 
wide area in the states of California (28), Washington (75), 



32 ECONOMIC GEOLOGY OF THE UNITED STATES 

and Oregon (56, 57). The separate fields are limited in ex- 
tent, widely separated, and with a small total output. Of 
the four fields recognized in Washington, the most impor- 
tant lie directly east of Seattle and Tacoma. The total 
thickness of coal-bearing sandstones and strata is about 
10,000 feet, but important coal beds are found only in the 
lower 2000 feet. It is stated that there are 100 coal seams 
of sufficient thickness to attract the prospector ; and in a 
single district there may be from 5 to 10 workable beds. 
Since the quality of the coal varies with the extent of 
dynamic disturbance, there is considerable variation even 
in a single field, and, in fact, in a single mine. 

Both California and Oregon produce small quantities of lignitic coal 
of Tertiary age, but show no promise of becoming important producers. 
Indeed, the coal-trade conditions of the Pacific coast are unique. The 
local supply is not equal to the demand, and the Rocky Mountain fields 
are too far off to supply the Pacific coast with cheap fuel. Therefore 
much coal is imported, bringing about a competition in San Francisco 
from many countries, including England, Wales, Scotland, Australia, 
Japan, and British Columbia. These foreign coals are all of better 
quality than the Pacific coast coals, and they can be imported with 
low freight rate as ballast in wheat-carrying vessels that come to San 
Francisco for cargoes. These coal imports form three-quarters of the 
total import coal tonnage of the United States; but since 1895 there 
has been a steady decrease in the importation of coal and an increase 
in the Pacific coast production. 

Alaska (23,24). — Although Alaskan coal was first mined 
in 1852 at Port Graham, the resources of the region are 
still but little known and slightly developed. The ex- 
plorations for gold during the last few years, together 
with the field work done by the United States Geological 



COAL 



33 



Survey, have proved that coal is widely distributed in the 
Alaskan Territory (Fig. 81). So far as known the coal 
beds are all in Mesozoic and Tertiary formations. While 
most of the coal is lignitic, there is considerable bitumi- 
nous coal and some semi-anthracite. 

Coal mining has been carried on at a number of localities, especially 
along the rivers and coast. The higher grade coals along the coast, par- 
ticularly in the southern part where shipments can be made throughout 
the year, will doubtless be developed with profit in the near future. 
Coals in the Yukon Valley, though of low grade and variable character, 
bring $15 a ton at the mines because of the local demand in the mining 
camps. The effect of such a local demand on the coal is even more 
strikingly shown by the fact that the semi-bituminous coal near the 
Cape Nome gold field sold, at times, for as much as $100 per ton. 

Production of Coal. — While coal mining in the United 
States began at an early date, the figures of production for 
the first few years are more or less incomplete. The phe- 
nomenal growth of the coal-mining industry is well shown, 
however, by the following figures : — 



Year 


Quantity 
Short Tons 


Year 


Quantity 

Short Tons 


1868 ...... 

1870 

1875 

1880 

1885 


31,648,960 
36,806,560 
52,288,320 
76,157,944 
111,159,795 


1890 

1895 

1900 

1903 ..... 


157.770,963 
193,117,530 
269,684,027 
357,356,416 



The production and value of the coal produced by the 
12 largest producers in point of output since 1901 has 
been as follows: — 



34 



ECONOMIC GEOLOGY OF THE UNITED STATES 





1901 


1902 


1903 


State 


Quantity 




Quantity 




Quantity 






Shokt 


Value 


Short 


Value 


Short 


Value 




Tons 




Tons 




Tons 




Pennsylvania : 














Anthracite 


67,471,667 


112,504,020 


41,373,595 


76,173,586 


74,607,068 


152,036,448 


Bituminous 


82,305,946 


81,397,586 


98,574,367 


106,032,460 


103,117,178 


121,752,759 


Illinois 


27,331,552 


28,163,937 


32,939,373 


33,945,910 


36,957,104 


43,196,809 


West Virginia 


24,068,402 


20,848,184 


24,570,826 


24,748,658 


29,337,241 


34,297,019 


Ohio 


20,943,807 


20,928,158 


23,519,894 


26,953,789 


24,838,103 


31,932,327 


Alabama 


9,099,052 


10,000,892 


10,354,570 


12,419,666 


11,654,324 


14,246,798 


Indiana 


6,918,225 


7,017,143 


9,446,424 


10,399,660 


10,794,692 


13,244,817 


Colorado 


5,700,015 


6,441,891 


7,401,343 


8,397,812 


7,423,602 


9,150,943 


Kentucky- 


5,469,986 


5,213,076 


6,766,984 


6,666,967 


7,538,032 


7,979,342 


Iowa 


5,617,499 


7,822,805 


5,904,766 


8,660,287 


6,419,811 


10,563,910 


Maryland 


5,113,127 


5,046,491 


5,271,609 


5,579,869 


4,846,165 


7,189,784 


Kansas 


4,900,528 


5,991,599 


5,266,065 


6,862,787 


5,839,976 


8,871,953 


Tennessee 


3,633,290 


4,067,389 


4,382,968 


5,399,721 


4,798,004 


5,979,830 



Grouping the output by fields, the overwhelming impor- 
tance of the Appalachian field is well seen. 

Production of Coal in United States by Fields from 
1901-1903 



Field 



Anthracite (Pa., Colo., N. Mex.) 

Triassic 

Appalachian 

Northern 

Eastern Interior 

Western 

Rocky Mt. . . 

Pacific Coast 



1901 
Short Tons 



67,538,536 

12,000 

150,501,214 

1,241,241 

37,450,871 

19,665,985 

14,090,362 

2,799,607 



1902 
Short Tons 



41,467,532 

39,206 

173,274,861 

964,718 

46,133,024 

20,727,495 

16,149,545 

2,834,058 



1903 
Short Tons 



74,679,799 

35,393 

185,600,161 

1,367,619 

52,130,856 

23,171,692 

16,981,059 

3,389,837 



The average price of anthracite coal, per short ton, in 
1903 was $2.04, while that of bituminous was $1.24. 



COAL 35 

The exports in 1903 amounted to 2,008,857 long tons of 
anthracite, valued at 19,680,044, and 6,303,241 long tons of 
bituminous, valued at $17,410,385. 

Production of Leading Coal-producing Countries 

Country Short Tons 

United States (1903) 357,356,416 

Great Britain (1903) ...... 257,974,605 

Germany (1903) 178,916,600 

Austria-Hungary (1902) 43,518,319 

France (1903) 38,583,798 

Belgium (1903) 26,312,805 

Russia (1902) 17,090,835 

Japan (1901) 9,861,107 

Production of Coke. — The quantity of coke now produced 
annually in the United States is very large, and there is 
an extensive demand for it in smelting operations. In 
1903 there were produced 25,262,360 short tons of coke 
from 39,410,729 short tons of coal, which gave an average 
yield of 64.1 per cent coke per ton of coal, with the aver- 
age value of 12.63 per ton coke. This quantity was supplied 
by 77,188 coke ovens, and over 50 per cent of the supply 
came from Pennsylvania. In addition 1,882,394 short tons, 
or 7.4 per cent of the total production, was made in by- 
product coke ovens, the approximate percentage of by- 
products obtained from a ton. of coal being: coal tar, 12.55 
gallons; ammonia liquor, 14.4 gallons; ammonium sulphate, 
17.6 pounds. 

REFERENCES ON COAL 

General. 1. Catlett, Amer. Inst. Min. Engrs., Trans. XXX : 559, 1901. 
(Coal outcrops.) 2. Bain, Jour. Geol. Ill: 616, 1895. (Structure 
of coal basins.) 3. Lesley, Manual of Coal and its Topography; 
Philadelphia, 1856. 4. Lesquereux, 2d Geol. Surv. Pa., Ann. Kept., 
p. 95, 1885. (Origin.) 5. Lyell, Amer. Jour. Sci. CLV : 353, 1843. 



36 ECONOMIC GEOLOGY OF THE UNITED STATES 

(Upright trees in coal.) 6. Moffat, Amer. Inst. Min. Engrs., 
Trans. XV: 819, 1887. (Change of mine prop to coal.) 7. Steven- 
son, Geol. Soc. Amer. Bull., V : 39, 1893. (Origin Pa. anthracite.) 
8. Wormley, Geol. Surv., Ohio, VI: 403, 1870. (Proximate and 
ultimate analysis.) See also Nos. 32, 32a, 37, 55. 
General Areal Reports. 9. Hayes, U. S. Geol. Surv., 22d Ann. 
Kept., Ill: 1, 1903. (U. S. coal fields.) 10. MacFarlane, Coal 
Regions of America, 700 pp., 3d ed., 1877, New York. 11. Nich- 
olls, The Story of American Coals, 1897 (Phila.). 12. White, U. S. 
Geol. Surv., Bull. 65. (Bituminous field, Pa., Ohio, and W. Va.) 
13. Series of papers on the several coal fields of the United 
States, in U. S. Geol. Surv., 22d Ann. Rept., Ill: 11-571, 1902, as 
follows: Ashley, p. 271. (Eastern Interior.) 14. Bain, p. 339. 
(Western Interior.) 15. Hayes, p. 234. (Southern Appalachians.) 
16. Smith, p. 479. (Pacific coast.) 17. Storrs, p. 421. (Rocky 
Mountain field.) 18. Stoek, p. 61. (Pa. anthracite.) 19. Taff, 
p. 373. (Southwestern.) 20. White, Campbell, and Hazeltine, 
p. 125. (Northern Appalachians.) — Alabama: 21. Gibson, Ala. 
Geol. Surv., 1890. (Cahaba field.) 22. McCalley, Ala. Geol. Surv., 
1900. (Warrior field.) —Alaska: 23. Ball, U. S." Geol. Surv., 17th 
Ann. Rept., 1 : 771, 1896. (Coal and lignite.) 24. Brooks, Ibid., 
22d Ann. Rept., Ill: 521. — Arkansas : 25. Taff, U. S. Geol. Surv., 
21st Ann. Rept., II: 313. (Camden field.) — Arizona : 26. Blake, 
Amer. Geol., XXI: 345, 1898. 27. Campbell, U. S. Geol. Surv., 
Bull. 225: 240, 1904. (Deer Creek field.) — California : See Pacific 
Coast Report referred to above and also various county reports in 
(28) 11th Ann. Rept. Calif. State Mining Bureau. — Colorado : 
29. Eldridge, U. S. Geol. Surv., Geol. Atlas of the U. S., folio 9. 
(Anthracite.) 30. Hills, U. S. Geol. Surv., Min. Res., 1892, 319. — 
Georgia: 31. McCallie, Ga. Geol. Surv., Bull. 4, 1904. (General.) 
— Iowa: 32a. Keyes, la. Geol. Surv., II: 1894. (General.) — Indi- 
ana: 32. Ashley, Ind. Dept. of Geol. and Nat. Hist., 23d Ann. 
Rept., 1899: 1. — Illinois: 33. Also Worthen and others, 111. 
Geol. Surv., 1 : 1866 ; III : 1868 ; IV : 1870 ; V : 1873 and VI : 1875. — 
Indian Territory : 34. Adams, Ibid., 21st Ann. Rept., II : 257, 1900. 
(Eastern Choctaw field.) 35. Taff, White, and Girty, U. S. Geol. 
Surv., 19th Ann. Rept., Ill : 423, 1898. (McAlester-Lehigh field.) — 
Iowa: 36. Keyes, Iowa Geol. Surv., II: 536. — Kansas: 37. Ha- 
worth and Crane, Kas. Univ. Geol. Surv., Ill: 13, 1898. — Ken- 
tucky: 38. Moore, Ky. Geol. Surv., Ser. 2, IV, pt. XI: 423. (Eastern 
border and Western field.) 39. Lesley, Ky. Geol. Surv., IV: 443, 
1858. (Eastern.) 40. Norwood, Ann. Rept., Inspector of Mines, 
1901-1902. (Much general information.) 41. For analyses, see 



COAL 37 

Ky. Geol. Surv., New Series, Chem. Rept., etc., pt. I, II, and III. — 
Louisiana : 42. Harris, Prelim. Rept. on Geol. of Louisiana for 
1899: 134. (Lignite.) —Maryland: 42a. Martin, Rept. on Alle- 
gheny Co. — Michigan : 43. Lane, Mich. Geol. Surv., VIII : pt. 2. — 
Missouri: 44. Winslow, Mo. Geol. Surv., 1891: 19-226. — Montana : 
45. Weed, Eng. and Min. Jour., LIII: 520, 542, and LV: 197, also 
Geol. Soc. Amer., Bull. 111:301, 1892. (Great Falls and Rocky 
Fork fields.) 46. Rowe, Amer. Geol., XXXII: 369, 1903. 
47. Burchard, U. S. Geol. Surv., Bull. 225:276, 1904. (Lignites, 
Upper Missouri Valley.) — Nebraska: 48. Barbour, Neb. Geol. Surv., 
I: 198, 1903. — Nevada: 49. Spurr, U. S. Geol. Surv., Bull. 225: 
289, 1904. — New Mexico: 50. Johnson, Sch. of M. Quart., XXIV: 
456. (Cerillos.) 51. Stevenson, N. Y. Acad. Sci., Trans. XV: 105, 
1896. (Cerillos field.) — North Carolina: 52. Woodworth, U. S. 
Geol. Surv., 22d Ann. Rept., Ill: 31, 1902. — North Dakota: 

53. Babcock, X. Dak. Geol. Surv., 1st Biennial Rept., 1901 : 56. 

54. Wilder, Eng. and Min. Jour., 74 : 674, 1902. (Lignite.) Ohio: 

55. Orton, Ohio Geol. Surv., VII: 253. —Oregon: 56. Diller, U. S. 
Geol. Surv., 17th Ann. Rept., I. (X. W. Ore.) 57. Diller, Ibid., 
19th Ann. Rept., Ill: 309. (Coos Bay.) — Pennsylvania: 58. d'ln- 
villiers, 2d Pa. Geol. Surv. Rept., 1885 and 1886. (Pittsburg re- 
gion.) 59. McFarlane, Coal Regions of America, 3d ed. ; New 
York, 1877. 60. Rept. MM. contains many analyses. 61. See also 
various county reports of same survey. 62. Final Summary Rept., 
Ill: pt. 1, and 2. — Rhode Island: 63. Emmons, Amer. Inst. Min. 
Eng., Trans. XIII : 510, 1885. 64. Stevenson, Manchester Geol. 
Soc, Trans. XXIII: 127. (New Eng. fields.) — South Dakota: 
65. Todd, S. Dakota Geol. Surv., Bull. 1 : 159. — Tennessee : 60. Duf- 
field, Eng. and Min. Jour., LXXIV : 442, 1902. (Cumberland Pla- 
teau.) 67. Safford, U. S. Geol. Surv., Min. Res., 497. 1892. — Texas: 
68. Dumble, Bull, on Lignites of Texas, Tex. Geol. Surv. (Lig- 
nites.) 69. Phillips, Univ. Tex. Mineral Surv., Bull. 3 : 137, 1902. 
(Coal and lignite.) 70. Vaughan, U. S. Geol. Surv., Bull. 164, 
1900. (Rio Grande fields.) — Utah : 71 . Forrester, U. S. Geol. Surv., 
Min. Res., 511, 1892. — Vermont: 72. Hitchcock, Amer. Jour. Sci., 
ii, XV: 95, 1853. (Lignite at Brandon.) — Virginia: 73. Camp- 
bell, U. S. Geol. Surv., Bull. Ill, 1892. (Big Stone Gap field.) 
74. Woodworth, U. S. Geol. Surv., 22d Ann. Rept., Ill: 31, 1902. 
(Triassic coal.) — Washington : 75. Landes and Ruddy, Wash. Geol. 
Surv., II; Willis, U. S. Geol. Surv., Ann. Rept., Ill: 393, 1898. 
(Puget Sound.) — West Virginia : 76. White, West Va. Geol. Surv., 
II: 1903. — Wyoming: 77. Fisher, U. S. Geol. Surv., Bull. 225: 293, 
1904. 78. Knight, Min. Ind., Ill : 145, 1894. 



38 



ECONOMIC GEOLOGY OF THE UNITED STATES 



REFERENCES ON PEAT 

79. Ries, N. Y. State Museum, 54th Ann. Kept., 1903. (N. Y., Origin 
and uses in general, Bibliography.) 80. Carter, Ont. Bur. Mines, 
Kept, for 1902. (General.) 81. Shaler, U. S. Geol. Surv., 12th 
Ann. Kept., p. 311. (Peat and swamp soils.) 82. Roller, Die 
Torfindustrie, Vienna, 1889. 83. Ries, Min. Res., U. S. Geol. Surv., 
1901. (U. S.) 



CHAPTER II 
PETROLEUM, NATURAL GAS, AND OTHER HYDROCARBONS 

Under this head are included a number of hydrocarbon 
compounds, of complex and variable composition, ranging 
from the solid to the gaseous state, the series including four 
well-marked and well-known members; viz., natural gas, 
petroleum, mineral tar or maltha, and asphalt. The de- 
velopment of these products, and especially the first two, 
has been so remarkable and attended by such important 
economic results that it seems well to preface the follow- 
ing description by a brief outline of this history of their 
development. 

History of Petroleum Development. — Petroleum has long 
been known in many parts of the world because of its pres- 
ence in bituminous springs or as a floating scum on the 
surface of pools. It was used at an early date on the walls 
of Babylon and Nineveh, and was obtained by the Romans 
from Sicily for use in their lamps. 

In the United States petroleum was mentioned by French 
missionaries even in 1635, and the early Pennsylvania settlers 
obtained small quantities by scooping out the oil from dug 
wells. Its discovery at greater depth on the western slope 
of the Alleghanies was made during the drilling of brine 
wells ; but its early use was chiefly a medicinal one until 
1883, when attempts were made to purify it for use as a 

39 



40 ECONOMIC GEOLOGY OF THE UNITED STATES 

lubricant and illuminant. The beginning of the oil industry 
is usually considered to date from the sinking of a successful 
well by Colonel Drake on Oil Creek, Pennsylvania, in 1860. 
From this center prospectors spread out in all directions mak- 
ing valuable discoveries, until now petroleum production and 
refining rank among the leading industries of the country, 
the supply coming from many states. 

History of Natural Gras Development. — Natural gas was 
discovered and first employed for economic purposes at 
Fredonia, New York, in 1824. In 1841 it was used in the 
Great Kanawah Valley as a fuel in salt furnaces, but its first 
extensive use began in 1872 at Fairview, Pennsylvania. It 
was used in 1885 for iron smelting at Etna Borough near 
Pittsburg, and in 1886 was piped nineteen miles from 
Murrayville to Pittsburg. Now natural gas is piped long 
distances to cities, being used as a fuel in many industries, 
as well as for domestic heating and lighting. 

Properties of Petroleum (1, 2, 7). — Crude petroleum is a 
liquid of complex composition and variable color and den- 
sity. It consists of a mixture of hydrocarbons, the American 
petroleum belonging usually to the paraffin series although 
some has an asphaltic base. The Mississippi River forms 
a rough dividing line between fields containing oil with a 
paraffin base and those with an asphaltic base. In addition 
to these compounds, petroleum may contain a small per- 
centage of nitrogen and sulphur. 

The following are analyses of several petroleums from 
American and foreign localities : — 



PETROLEUM, NATURAL GAS, OTHER HYDROCARBONS 41 
Elementary Analyses of Petroleums 



Locality 





Per Cent 




c. 


H. 


O. 


83.5 


13.3 


3.2 


84.3 


14.1 


1.6 


84.9 


13.7 


1.04 


82.0 


14.8 


3.2 


84.0 


13.4 


1.8 


80.4 


12.7 


6.9 


82.2 


12.1 


5.7 


86.3 


13.6 


0.1 


86.6 


12.3 


1.1 


87.1 


12.0 


0.9 


86.8 


13.2 





Specific 
Gravity 
H 2 = 1 



Heavy oil, W. Va. 
Light oil, W. Va. , 
Heavy oil, Pa. 
Light oil, Pa. . . 
Parma, Italy . . 
Hanover, Germany 
Galicia, Austria . . 
Light oil, Baku, Rus. 
Heavy oil, Baku, Rus. 

Java 

Beaumont, Texas . 



.873 

.8412 

.S86 

.816 

.786 

.892 

.870 

.884 

.938 

.923 

.920 



Petroleums commonly vary in specific gravity between 
.801 and .965, the following being some of the limits shown 
by American oils : — 

Specific Gravity of Some American Petroleims 



State 


Specific Gravity 


Gravity Beai me 1 


Pennsylvania .... 

Ohio 

Kansas 

West Virginia .... 
Beaumont, Texas . . . 

Wyoming 

California 










.801-.817 

.816-.860 

.835-1.000 

.841-.873 

.904-.925 

.912-.945 

.920-.983 


46.2-42.6 
42.8-32.5 
38.8-10.0 
37.6-30.0 
24.8-31.1 
23.3-11.9 
21.9-12.3 



The temperature at which crude petroleum solidifies ranges 
from 82° F., in some Burma oils, to several degrees below 
zero in certain Italian oils. The flashing point, or the lowest 

1 A specific gravity of 1, compared with water, is 10° on the Beaunie scale. 



42 



ECONOMIC GEOLOGY OF THE UNITED STATES 



temperature at which inflammable vapors are given off, 
may be as low as zero degrees in the Italian oils to as high 
as 370° F. in an oil found on the Gold Coast of Africa, but 
these are extreme limits. There is also a great range in the 
boiling point, which is 180° F. in some Pennsylvania oils and 
338° F. in oils found at Hanover, Germany. 

The various liquid hydrocarbons making up crude petro- 
leum vary in their gravity and temperature of volatilization. 
The more important oils which can be separated from crude 
petroleum by distillation are gasoline, benzine, heavy naphthas, 
and residuum. Those with a paraffin base are generally 
lighter and more valuable on account of the higher quantity 
and quality of the naphthas, illuminating oils, and lubricating 
oils which they produce. Those with an asphalt base are of 
inferior quality and chiefly valuable for fuel. Their trans- 
portation by pipe lines is also more difficult. 

The percentage of the different distillates varies. 

The following average percentages of distillates were 
yielded by the oils of several fields in 1902 (Oliphant) : — 





Appalachian 
Field 


Lima, Ind. 
Field 


Kansas 
Field 


Naphthas 

Illuminating oils 

Lubricating and heavy oils . . 

Residuum 

Loss from uncondensed products 
and water 


20.1 

61.4 

7.1 

6.3 

5.1 


10.9 
48.8 
17.2 

23.0 


18 
30 
25 

27 



Properties of Natural Gas. — This consists chiefly of Marsh 
gas — fire damp — CH 4 . It is colorless, odorless, and burns 
easily, as well as somewhat luminously; but when mixed 



PETROLEUM, NATURAL GAS, OTHER HYDROCARBONS 43 

with air, it is highly explosive. As is shown by the fol- 
lowing analyses, several other gases are commonly present 
in small quantities : — 

Analyses of Natural Gas 











Car- 


Car- 






Sul- 




Hydro- 


Marsh 


Olefi- 


bonic 


bonic 


OXYGEN 


Nitro- 


phuric 




gen 


Gas 


ant Gas 


Oxide 


Acid 




gen 


Hydro- 
gen 


Fostoria, 0. 


1.89 


92.84 


.20 


.55 


.20 


.35 


3.82 


.15 


Findlay, 0. 


1.64 


93.35 


.35 


.41 


.25 


.39 


3.41 


.20 


Muncie, Ind. 


2.35 


92.67 


.25 


.45 


.25 


.35 


3.53 


.15 



Mode of Occurrence (4,5,6,8). — Oil is rarely found without 
gas, and saline water is likewise often present. If the con- 
taining strata are horizontal, the oil and gas are usually 
irregularly scattered, but if tilted or folded, they collect at 
the highest point possible. It was the result of observa- 




a GAS 



6 OIL 



d CAPROCK 



Fig. 13. — Section of anticlinal fold showing accumulation of gas, oil, and water. 
After Hayes, U. S. Geol. Surv., Bull. 212. 

tions along this line that led I. C. White to develop what 
is known as the "Anticlinal Theory" (8). According to 
this theory, in folded areas the gas collects at the summit 
of the fold, with the oil immediately below, on either side, 
followed by water (Fig. 13). Unless there are secondary 



44 ECONOMIC GEOLOGY OF THE UNITED STATES 

anticlines, the intervening synclines are liable to be barren 
of oil and gas. For this theory, as for others, it is necessary 
that the oil-bearing stratum shall be capped by a practically 
impervious one. 

Such anticlinal waves are found in the oil fields of the 
Appalachians, Indiana, western Ohio, and many other locali- 
ties. While this theory has been disputed, it may be con- 
sidered established for many localities. The rival theory 
advanced by Lesley and Ashburner, that the oil has accumu- 
lated in porous areas of rock, perhaps ancient shore-line 
deposits, may likewise apply in some cases. It supplies all 
the necessary conditions of a subterranean reservoir for the 
accumulation of oil in "pools." 

In the first discovered fields, the oil and gas were 
found in porous, sandy strata, varying from fine-grained, 
cemented sandstone to loose gravels. These strata were 
termed sands, and the area of porous oil sand was called 
the pool. Later discoveries in Ohio and Indiana showed 
that the gas and oil might occur in limestone also. 

The quantity of oil which a cubic foot of apparently dense 
rock can hold is often surprising. White (36) estimated 
that fairly productive sands may hold from six to twelve 
pints of oil per cubic foot, but that probably not more than 
three-fourths of the quantity stored in the rock is obtain- 
able. The ease with which the containing rock yields its 
supply of oil depends largely on the openness of the pores. 

Pressure of Oil and Gas Wells. — Since both oil and gas 
usually occur in the earth under pressure, any break in the 
porous rock or reservoir which contains them allows them 
to escape, frequently giving rise to surface indications, and 
the force with which oil and gas oftentimes issue from a 



PETROLEUM, NATURAL GAS, OTHER HYDROCARBONS 45 

well indicates the pressure under which they are confined. 
It is sometimes sufficient to blow out the drilling tools and 
casing, as well as to cause the oil to spout many feet into 
the air. 

There are several remarkable cases of the amount spouted by these 
gushing wells. One of these is the famous Lucas well at Beaumont, 
Texas, which in 1901 for nine days gushed a six-inch stream to a height 
of 160 feet, at the rate of 75,000 barrels per day. This, however, is 
small compared with the records of some Russian oil wells. Although 
many wells flow when first drilled, this does not usually continue long, 
and the oil then has to be brought to the surface by pumping. The depth 
of the wells drilled in the United States ranges from 250 to 3700 feet, 
and over 70 per cent of the total number drilled are located in Ohio 
and Pennsylvania. 

The maximum pressure which a well develops when closed 
has been called rock pressure. As a result of his studies 
in the Ohio-Indiana field, Orton (29) found that the rock 
pressure was the same as that of a column of water whose 
height was equal to the difference in elevation between the 
level of Lake Erie and that of the oil or gas bearing stratum. 
He therefore considered it to be hydrostatic pressure. This 
theory, while apparently applicable in many localities, was 
found to be inadequate to explain the great pressure shown 
in many shallow wells. In such cases, no doubt, as in many 
others, the pressure is due to the expansive force of the 
imprisoned gas. 

Either the drilling of additional wells or a drain by exces- 
sive use from wells already bored commonly causes a slow 
decrease in pressure in an oil or gas field. Thus in the 
natural-gas region of Findlay, Ohio, the rock pressure in 
1885 was 450 pounds per square inch; 400 in 1886; 360- 
380 in 1887; 250 in 1889; 170-200 in 1890. Some West 



46 ECONOMIC GEOLOGY OF THE UNITED STATES 

Virginia wells have shown a measured rock pressure of 
1110 pounds per square inch and an estimated pressure of 
2000 pounds. 

Origin. — That the solid, liquid, and gaseous hydrocarbons 
are more or less closely related is evident from the fact that 
the gases given off by petroleum are similar to those pre- 
dominating in natural gas, while the exposure of many 
petroleums to the air results in a change to a viscous mass 
and finally to a solid, asphalt-like substance. It is a well- 
known fact that petroleum is rarely free from natural gas, 
although this gas may sometimes form alone, as in coal 
mines, or from decaying vegetation in stagnant pools. The 
origin of the hydrocarbon compounds has been the subject 
of much speculation among both chemists and geologists, the 
former for a time arguing for an inorganic or mineral origin, 
the latter for an organic derivation. 

Inorganic Theory. — Several theories have been advanced 
to account for an inorganic origin of oil, the most important 
of which, though not the earliest, was that of Mendeljeff, 
the Russian chemist. According to his theory, the interior 
of the earth contains metallic iron, as well as carbid of iron 
like that found in meteorites. Waters percolating down- 
ward through the earth's crust, on reaching the heated 
interior, become converted into steam, which, attacking the 
carbid of iron, forms hydrocarbons. These are forced to the 
surface by the expansive force of the steam. 

From a purely chemical standpoint, this theory is reason- 
able, but it does not accord with geologic facts. If petro- 
leum were found in this manner, we should expect to find it 
widely distributed through the oldest rocks of the earth's 



PETROLEUM, NATURAL GAS, OTHER HYDROCARBONS 47 

crust. On the contrary, it is known in these rocks at only 
one locality, in Ontario, where a hard, compressed asphalt 
is found in crystalline rocks. It is significant that this 
material, which was probably originally petroleum, occurs 
in rocks which show evidence of having been originally 
stratified. 

Organic Theory. — This considers that petroleum has been 
derived from either animal or vegetable matter by a process 
of slow distillation, although the exact changes involved are 
uncertain. There are several strong arguments in favor of 
it. (1) Petroleum is a combustible substance, and all other 
similar combustibles have originated organically. (2) It is 
possible to artificially produce, from either animal or vege- 
table substances, both gaseous and liquid compounds which 
are closely analogous to those found in petroleum and 
natural gas. Fish oil, for example, will on distillation yield 
petroleum compounds, including illuminating oil, lubricating 
oil, benzine, and paraffin. (3) These substances occur in 
fossil-bearing rocks. (4) They are practically absent from 
the crystalline rocks. (5) In some places these substances 
occur in close proximity to fossils. (6) Natural gas is 
actually generated in coal seams. 

Some geologists, including Orton (4) and Newberry (Geol. 
Soc. Amer., Bull. I: 192), have believed that the formation of 
petroleum has taken place at low temperatures ; but others, 
including Peckam (6), have considered heat necessary. In 
the case of Appalachian oils, the folding of the strata is sup- 
posed to have supplied this heat. 

It seems doubtful whether either petroleum or natural gas 
have migrated any great distance through the strata subse- 
quent to their formation. When any movement has taken 



48 ECONOMIC GEOLOGY OF THE UNITED STATES 

place through pores of the rock, it has probably been due to 
gravity separation, the gas rising to the highest point of the 
stratum while the oil settles. 

Geological Distribution of Petroleum and Natural Gas. — 

Petroleum is widely distributed geologically, being found in 
rocks whose age ranges from the Ordovician to the most 
recent, the occurrences in Paleozoic strata being chiefly in 
eastern United States, those in post-Carboniferous strata in 
the western and southern states. 

Natural gas may show an equally wide geological distribu- 
tion, although in the United States the larger amount is now 
obtained from the Paleozoic formations. 

Distribution of Petroleum in the United States. — The im- 
portant petroleum occurrences of the United States, so far as 
at present known, may be considered to belong to the seven 
following fields (Fig. 14) : (1) the Appalachian field, includ- 
ing New York, western Pennsylvania, eastern Ohio, West 
Virginia, Kentucky, and Tennessee ; (2) the Ohio-Indiana 
field ; (3) the Texas-Louisiana field ; (4) the Kansas-Indian 
Territory field; (5) the Colorado fields; (6) the Wyoming 
fields; (7) the California fields. In addition to these there are 
scattered occurrences in Michigan, etc. (See map, Fig. 14.) 

Appalachian Field. — This field, which supplied over 85 per 
cent of the oil produced in the United States in 1902, extends 
from southwestern New York (25) into West Virginia (37, 38) 
and is subdivided into several districts, each containing sev- 
eral "pools." The region is of interest historically and geo- 
logically, some of the earliest discoveries of oil having been 
made in it. The oil is obtained from sandstones and con- 
glomerates, ranging in age from the Upper Carboniferous 



Plate III 




Fig. 1. — General view of Tuna Valley, in Pennsylvania oil tit 

Oliphant. 



Photo, by F. II. 




Fig. 2. — View in Los Angeles, Calif., oil field. Such close spacing of oil derricks 
tends to hasten the exhaustion of the oil supply. 



PETROLEUM, NATURAL GAS, OTHER HYDROCARBONS 49 



in the upper part of the field, to Middle Devonian in the 
lower portion, which underlie an area of probably 55,000 




^ tfi 



~ - 
8 >, 



square miles. There are often several productive beds in a 
single formation, and 40 oil sands have been recognized in 



50 



ECONOMIC GEOLOGY OF THE UNITED STATES 



the entire section. This field, which is the most important 
in the United States, supplies a large amount of high-grade 
petroleum, and has a large output ; but apparently the pro- 
duction has practically reached its maximum. The petroleum- 
producing areas of Pennsylvania (31, 32) are divided into a 
number of districts, this division being based partly on quality 
and partly on county lines. Each district may be subdivided 
into pools. In the Clarendon and Warren County district 
is found some of the finest petroleum produced in the United 




TRENTON 
LIMESTONE 



Fig. 15. 



UTICA 
SHALE 



HUDSON R. NIAGARA LIMESTONE LOWER UPPER 

SHALE NIAGARA SHALE HELDERBERG HELDERBERG 

MEDINA CLINTON LIMESTONE LIMESTONE LIMESTONE 



OHIO 
SHALE 



Geological section of Ohio-Indiana oil and gas fields. After Orton. 
U.S. Geol. Surv., 8th Ann. Rept., II. 

States, while the Franklin district is noted for the fine, natu- 
ral lubricating oil which it yields. In Kentucky (22) and 
Tennessee a limited amount of petroleum is obtained from 
Silurian rocks. The total number of wells drilled in the 
Appalachian field from 1877 to the end of 1903 was 137,679. 
Ohio-Indiana Field (16-18, 26-30). — The discovery of oil 
and gas in the Trenton rocks of western Ohio in 1884 caused 
considerable excitement, since it showed the existence of 
petroleum in limestone, an exception to previously known 
conditions, and at a much lower geological horizon than any 
in which oil or gas had hitherto been found. This field 



Plate IV 




PETROLEUM, NATURAL GAS, OTHER HYDROCARBONS 51 



extends from Findlay in northwestern Ohio southwestward 
into Indiana. The oil, which is dark and heavy, and con- 
tains, a higher percentage of sulphur than the Pennsylvania 
oil, is found near the top of the porous, dolomitized portions 
of the Trenton limestones, at depths of about 1100 feet. 
The limestone, which shows several low folds (Fig. 15), is 
covered by the impervious Hudson River shales. 

Texas- Louisiana Oil Fields (33-35). — These occur in a belt 
from 50 to 75 miles wide along the Gulf Coast from near the 
Mississippi River in Louisiana to a point about two thirds 
the way across Texas (Fig. 14). The nearly flat surface of 
this coastal plain 
is occasionally in- 
terrupted by low 
mounds or swells 
which seem to in- 
dicate favorable 
conditions for the 
accumulation of oil 
below the surface. 
Underlying this 
area is a series of 
Quaternary and Tertiary clays, sands, and gravels, with 
occasional limestones, having in general a gentle southeast- 
ern dip interrupted by low domes. 

The oil pools are all of small size, that at Beaumont, which 
is the best known, covering an area of about 200 acres 
(PI. IV). It was discovered in 1901, and within a year 
and a half 280 successful wells had been drilled. The oil 
rock, which lies from 900 to 1000 feet below the surface, is 
a very porous, crystalline dolomitic limestone, and the cap- 




SALT 



m 

SAND 



m m 

SHALE. GTPSUM 



Fig. 16. — Section of Spindle Top oil field near Beau- 
mont, Texas. After Fenneman, Min. Mag., XI: 317. 



52 ECONOMIC GEOLOGY OF THE UNITED STATES 

rock is clay. The occurrence of gypsum and salt under- 
lying the oil rock in some of the wells is unique (Fig. 16). 
Many of the wells in this pool were gushers, but so great was 
the drain on this field that by the end of the first year after 
its discovery the pressure was considerably reduced, and in 
1903 many of the wells had practically ceased producing, 
while others were yielding a mixture of salt water and oil. 
The production, however, is still considerable, although the 
supply is no doubt exhaustible. The coastal-plain oils have 
an asphaltic base, or are " heavy," and at times contain con- 
siderable sulphur. 

In 1903 many wells were being developed in the Sonr Lake district 
about 20 miles northwest of Beaumont. The oil is heavy like that of 
Beaumont, but runs lower in sulphur. In Louisiana active drilling 
operations have been carried on in the region around Jennings, and one 
well yielded 20,000 barrels per day while it was gushing. The oil re- 
sembles that of Beaumont. 

The belt of Cretaceous rocks of central Texas has yielded both oil and 
gas at several localities, but the only important one is at Corsicana, where 
both a light and heavy oil have been found in sands interbedded with 
dense clay shales. The two kinds of oil occur at different horizons. 

Kansas (19-21). — In southeastern Kansas a dark green 
oil is obtained from the sugar sands near the bottom of the 
Cherokee shales, about 800 feet below the surface. A second 
horizon is found about 300 feet lower. 

California. — There are a number of productive fields in 
California (10-12), all lying south of the latitude of San Fran- 
cisco. Altogether there are 10 or 12 horizons in the folded 
Tertiary strata, which have a total thickness of 20,000 feet. 
The oil which is found in conglomerates, sandstones, and 
arenaceous shales, is, in the most productive areas, found 
closely associated with anticlines, but the strata are in many 



PETROLEUM, NATURAL GAS, OTHER HYDROCARBONS 53 




Fig. 17. — Section in Los Angeles oil field. 
After Watts, Calif. State Min. Bureau, 
Bull. 11 : 7, 1897. 



places extensively faulted (Fig. 17), and it is doubtless to 
these faults that many of the California oil springs are due. 
By adding to the. porosity of the rocks, the faulting has 
probably also increased the capacity of some of the oil 
reservoirs. 

In 1903 the Kern River field was the most productive 
in California. It has an area of 12 square miles, the oil 
being found at depths 
ranging from 200 to 300 
feet in a series of lower 
Miocene sands inter- 
bedded with clay. The 
wells yield from a few 
barrels up to 600 per 
day, but are flowing usually for only a short period. 

The California oils, like those of Texas, have an asphaltic 
base, those found in the shale being generally lighter. 

Wyoming (39-41). — This state contains 18 oil districts, 
most of which are but slightly developed and the geology 
imperfectly known. Most of them are in the Mesozoic 
strata, the balance in Upper Carboniferous, the oil being 
commonly found along the axes of anticlinal folds. The 
wells vary from 300 to 1500 feet in depth, and the oils 
are mostly lubricating, although a few contain considerable 
kerosene (39). 

Colorado. — The oil at Florence (13, 15), in this state, is 
found in porous, sandy layers of Cretaceous age, at depths 
of from 1000 to 2000 feet, and, unlike most other occur- 
rences, in a synclinal trough. It is a heavy oil. Near 
Boulder (14) there is another oil field, recently developed, 
in which the oil is found at depths as great as 8800 feet. 



54 ECONOMIC GEOLOGY OF THE UNITED STATES 

Alaska. — Petroleum has been found at several localities 
in Alaska (Fig. 81), and the developmental work already 
clone gives promise of a supply in the future (9,10). 

Distribution of Natural Gas in the United States. — The 

distribution of natural gas is almost coextensive with that 
of petroleum, but the commercially important fields are 
fewer in number. The most important producing states are 
New York (51), Pennsylvania (54), Ohio (53), Indiana (45), 
and Kansas (47). 

New York. — Gas is found in several formations, includ- 
ing the Medina and Oswego sandstones, Utica shale, and 
Potsdam sandstone, but the main supply is irregularly 
distributed through the Trenton limestones, showing no 
arrangement in belts or relation to folds. The pressure 
ranges from 10 or 20 pounds up to 1540 pounds, which is 
the highest reported from any field in the world. A simi- 
larly wide range exists in the volume of the wells. 

Pennsylvania. — Gas is obtained from the same forma- 
tions that carry the oil. The Bradford district was the 
first developed, and formerly yielded gas of high pressure. 
Much is still obtained from McKean, Elk, and Warren 
counties. Extensive deposits were also found about Pitts- 
burg, and later to the south of it. Green and Washington 
counties now produce important supplies from a pool whose 
length is about 25 miles and width 3 to 4 miles, with pres- 
sure ranging from 800 to 1000 pounds. Although in recent 
years several new gas-bearing sands have been discovered 
in southwestern Pennsylvania, the enormous demand for 
the gas threatens exhaustion of the available supply at no 
very distant date. 



PETROLEUM, NATURAL GAS, OTHER HYDROCARBONS 55 

West Virginia (see Petroleum references). — This state 
is now the leading producer of natural gas in the United 
States, and is looked to as an important source of future 
supply for both Ohio and Pennsylvania, whose gas supply 
is slowly falling off. The main supply is obtained from 
the Gordon and Fifth sands of the Cat skill formation, 
this being a higher horizon than that yielding the gas in 
the Bradford district of Pennsylvania. Immense quantities 
are obtained from the fields of Wetzel and Tyler counties, 
the wells being from 2700 to 3200 feet deep. Pipe lines 
are now run from this district to Pittsburg, and a line 
has been laid from Tyler County to Cleveland, Ohio. Un- 
fortunately, by allowing it to escape with the petroleum, 
many thousand cubic feet of gas have been wasted in this 
state. 

Ohio (52-53). — The Trenton limestone, which formerly 
supplied large quantities of natural gas, is now so nearly 
exhausted that little gas is obtained except by pumping. 
Some gas is obtained from the Clinton limestone of central 
and eastern Ohio, and small amounts from the Corniferous 
limestone ; but many towns in this state are now supplied 
by the West Virginia fields. 

Indiana (45,46). — The gas fields of this state, covering 
about 2500 square miles, were formerly among the most' 
important in the country, the gas being obtained from the 
Trenton limestone. The supply is, however, rapidly giving 
out, and its complete exhaustion is probable at no very 
distant date. 

Kansas (47-50). — Southeastern Kansas and northern Indian 
Territory are underlain by what is probably an extensive 
field of shale gas. The supply comes from the Cherokee 



56 ECONOMIC GEOLOGY OF THE UNITED STATES 

shale, and is now much used as a source of fuel in the local 
metallurgical and manufacturing industries. 

Some gas is obtained from eastern Kentucky. Scattered 
pockets of high -pressure gas have also been found at several 
localities in Texas and also in California. 

Uses of Petroleum. — The two most important uses are 
for illuminating and lubrication; but the various distillates 
have special uses. Rhigolene is used as a local anaesthetic, 
gasoline is used as a fuel, and naphtha as a solvent for 
resins in making varnish and in oilcloth manufacture, while 
benzine is of value for cleaning and as a substitute for 
and an adulterant of turpentine. Astral oil and mineral 
sperm oil are special grades of illuminating oil with high 
flashing points. Crude petroleum is now much used for 
fuel purposes in engines, as along the Pacific coast and 
in the southwest, where good coal is so scarce that many of 
the locomotives are run by the use of crude oil. 

The paraffin residue is placed on the market for medicinal 
purposes under the name of vaseline, petroleum ointment, 
and cosmoline. It is also used in the manufacture of chew- 
ing gum and for electrical insulation. 

Uses of Natural Gas. — Natural gas is widely employed 
as a fuel in factories, metallurgical establishments, glass 
works, cement plants, etc. For domestic purposes, such as 
heating, cooking, and lighting, it is also widely used. Its 
cheapness, cleanliness, and high calorific power, and the 
ease with which it can be used have been important factors 
in insuring its widespread selection for the above purposes. 

Oil Shales (55 a and b). — Shale containing sufficient petro- 
leum to permit its extraction by a process of distillation is 



PETROLEUM, NATURAL GAS, OTHER HYDROCARBONS 57 

known as torbanite or kerosene shale. Such shales are found 
in the Carboniferous of New South Wales, Australia, New 
Zealand, and Scotland, and in the Cretaceous of Brazil. 
They are almost unknown in the United States. The fol- 
lowing analysis indicates the composition and richness of 
shale in hydrocarbons : — 







Moist 


Volatile 
Hydro- 
carbon 


Fixed 
Carbon 


Ash 


Sulphur 


Rich shale, Joadja, N.S.W. . 


.16 


89.59 


5.27 


4.96 


.384 





The oil can be obtained by distillation in retorts ; but in view of 
the large available supplies of petroleum, obtainable in many parts 
of the world, the material at present has but little commercial value. 
It is distilled in New South Wales and also in Scotland. 



SOLID BITUMENS 

Occurrence (56-60, 66). — Solid bitumens may be grouped 
according to their mode of occurrence, as (1) asphaltites, 
which represent the varieties free from sandy and clayey 
impurities, found filling either fissures or basins ; (2) bitu- 
minous rocks, in which the bitumen fills the pores of sand- 
stones, limestones, or other rocks. They are found over a 
wide range (Fig. 18), both geographically and geologically. 

A study of the deposits leads to the conclusion that these 
solid bituminous compounds have been derived from petro- 
leum (58, 59, 60), for the following reasons : In the asphal- 
tite deposits the solid bitumens are often associated with 
petroleum springs, or with fissures leading down to or 
toward petroleum-bearing strata. In some cases the asphal- 
tite not only fills such a fissure, but impregnates the wall 



58 



ECONOMIC GEOLOGY OF THE UNITED STATES 



rock to a distance of a foot or two on either side of the 
vein, indicating that the material came up through the 
fissure in a liquid condition, filling it, and even penetrating 
the wall rock. 

The bitumen in bituminous rocks may either have origi- 
nated from organic remains within the rock itself or have 
seeped into it from some neighboring pool. In either case 
the material seems originally to have been liquid petroleum 
which later solidified. 




Fig. 18. —Map of asphalt and bituminous rock deposits of United States. After 
Eldridge, U. S. Geol. Surv., 22d Ann. Sept., IX. 



Asphaltites. — There are several varieties of asphaltites, 
all black or dark brown in color, commonly with a pitchy 
odor, burning readily with a smoky flame, and insoluble in 
water, but soluble in ether, oil of turpentine, and naphtha. 
Their specific gravity ranges from 1 to 1.1. They are 



PETROLEUM, NATURAL GAS, OTHER HYDROCARBONS 59 

closely related chemically and in their mode of occurrence, 
but differ somewhat in their behavior toward solvents, as 
well as in their fusibility. The most important varieties 
are described below. 

Albertite (61), a black bitumen with a brilliant luster and conchoidal 
fracture, a hardness of 1 to 2 and specific gravity 1.097, is found filling- 
fissures in bituminous shales in Xew Brunswick. 

Anthraxolite (63) is a coaly, lustrous, black mineral, with a hardness 
of 3 to 4, and specific gravity of 1.965. It is found at Sudbury, Ontario, 
forming veins in a black fissile slate, but has also been described from 
other localities. 

Ozokerite (67), also termed mineral wax or native paraffin, is a waxlike 
hydrocarbon, yellow brown to green, translucent when pure, and of 
greasy feel. Its specific gravity is .955. While known to occur in Utah, 
the most important deposit is in Galicia. At the latter locality the 
Ozokerite is found forming veins from a few millimeters up to several 
feet in thickness in much-disturbed Miocene shales and sandstones. 

Grahamite (66) is a vein asphalt found in the Carboniferous of West 
Virginia. 

Lake Asphalt (71) is not found in the United States, but occurs in the 
famous pit or lake on the island of Trinidad, off the coast of Venezuela. 

Uintaite, or Gikonite (66), is a black, brilliant 

bitumen, with conchoidal fracture, hardness 2 to 

2.5, and specific gravity of 1.065 to 1.07. It is 

found filling a series of fissures, termed veins, in 

the Bridger beds of the Tertiary in eastern Utah, 

and, to a less extent, in western Colorado. One 

of these veins, the Duchesne, has been worked to 

a depth of 105 feet, and is traceable for about a 

mile, its width for half this distance being 3 to 4 

feet. It is usually vertical and in places faulted. 

Manjak is the name applied to a bitumen 

rF Fig. 19. -Section of Gil- 

resemblmg Uintaite, found on the island of sonite vein, Utah. 

Barbados. It is a hydrocarbon of high puritv, After Eldrid ^^ u - s - 

J ° F Geol. Surv., 17th 

black color, brilliant luster, and conchoidal frac- Ann. Eept., I: 932. 




60 



ECONOMIC GEOLOGY OF THE UNITED STATES 



ture, and forms seams from a quarter of an inch to 30 feet thick in 
a blue shale. The material brings $60 a short ton in New York. 

Bituminous Rocks (66). — These are commonly classified 
according to the character of the containing rock, as bitu- 
minous sandstones, bituminous limestones, and bituminous 
schists. They are much more widely distributed than the 
asphaltites, being found in several geological horizons, and 
are worked in Kentucky (66), Indian Territory (66), and 
California (64). 

As illustrative of its mode of occurrence, we may men- 
tion the bituminous sandstone, which is extensively quar- 
ried near Santa Cruz, California (PI. V, Fig. 1). The 
rock, which is of blackish or brownish-black color, weather- 
ing to gray, occurs beneath the Monterey shales, sometimes 
resting directly on granites. The bitumen impregnates 
the heavy bedded sandstone immediately under the shale, 
and also the sand that fills cracks which extend up into 
the shale. These cracks, which vary in width from very 
minute size up to 25 or 30 feet, are sometimes traceable 
for several hundred feet, being at times of value as guides 
in finding the main bed. 

Analyses. — The variable composition of asphaltites and 
bituminous rocks can be seen from the following table : — 

Analyses of Asphaltites and Maltha 



Locality 


Soluble in 

CS 2 


Mineral 
Matters 


Non-bituminous 
Organic Matter 


Trinidad Lake Asphalt . 
Grahamite, W. Va. . . 
Gilsonite, Utah . . . 
Maltha, Kern. Co., Calif. 


54.25 
100.00 
100.00 

93.20 


36.51 

.10 

5.77 


9.24 
.54 



Plate V 




Fig. 1. — Quarry of bituminous sandstone, Santa Cruz, Calif. After Eldridge, U.S. 
Geol. Surv., 22d Ann. Rept., I. 




Fig. 2. — Granite quarry, HardVick, Vt. Photo, by G. H. Perkins. 



PETROLEUM, NATURAL GAS, OTHER HYDROCARBONS 61 
Analyses of Bituminous Rocks 



Locality 


Moisture 


Soluble 

inCS 2 


CaC0 3 


MgCOg 


Sand or 
Clay 


California 

Kentucky 

Seyssel, France . . . 
Limmer, Germany . . 


2.50 


20.20 
5.76 
8.15 

18.26 


3.00 

91.70 
56.50 


27.01 


74.00 

94.22 

4.98 



Uses. — Trinidad asphalt mixed with powdered rock and 
tar is much in use for pavements, and the bituminous rocks 
are employed for similar purposes. Ozokerite, known as 
Ceresin in its purified form, is used in the manufacture of 
candles, ointments, powders, as an adulterant of bees- 
wax, and combined with India rubber as an insulating 
material. 

The most important use of Uintaite and Manjak is for 
making low-grade and dipping varnishes, such as are used 
for iron work and baking Japans. Other uses to which 
the Uintaite at least has been put are for preventing elec- 
trolytic action on iron plates of ship bottoms, coating 
masonry, acid-proof lining for chemical tanks, roofing pitch, 
insulating electric wires, as a substitute for rubber in com- 
mon garden hose, and as a binder pitch in making coal 
briquettes. 

Production of Petroleum, Natural Gas, and Asphaltum. — 
The production of crude petroleum and natural gas for 
several years is given below : — 



62 



ECONOMIC GEOLOGY OF THE UNITED STATES 





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PETROLEUM, NATURAL GAS, OTHER HYDROCARBONS 63 
Value of Petroleum and Natural Gas produced en 1903 



State 


Value of 
Petroleum 


Value of 
Natural Gas 


Combined 
Value 


Pennsylvania . . . 

Ohio 

West Virginia . . . 

Indiana 

California 

Texas 

New York 

Other states .... 


$18,170,881 

26,234,521 

20,516,532 

10.474,127 

7,399,349 

7,517,479 

1,849,135 

2,532,026 


$16,182,834 

4,479.040 

6,882.359 

6,098.364 

104,521 

21,351 

493,686 

1.553.205 


$34,353,715 

■ 30,713.561 

27,398,891 

16.572.491 
7,503,870 
7.538.830 
2.342.821 
4,085,231 


Total 


$94,694,050 


835,815,360 


$130,509,410 



The average price per barrel of petroleum naturally 
varies somewhat from year to year. In 1885 it was 87-J^; in 
1890, 86|^; in 1895, I1.36J; in 1900, 81.194; in 1903, 94 j£ 

The total number of barrels of petroleum produced in the 
United States from 1859 to the end of 1903 was 1,265,751,585, 
while the total value of the natural gas produced in the 
United States from 1885 to the end of 1903 was $322,872,792. 

The world's production of petroleum in 1902 and 1903 
was as follows : — 



World's Production of Petroleum in 1902 and 1903 



Country 

United States . . . . 

Russia 

Sumatra, Java, Borneo . 

Galicia , 

Roumania 

India , 

Japan 

Canada , 

Germany , 

Peru 

Italy , 

All other countries . . 
Total 



Barrels, 1902 


Barrels, 1903 


69,389.194 


100,461,337 


85,168,556 


75,591,256 


3,038,700 


6,640,000 


3,251.544 


5.234,475 


1,406,160 


2,763,117 


1,430,716 


2,510,259 


1,100,000 


964,000 


572,500 


481,504 


313,630 


445,818 


72,261 


61,745 


10,100 


20,000 


20,000 


30.000 


165,773,361 


195,203,511 



64 ECONOMIC GEOLOGY OF THE UNITED STATES 



Exports of Mineral Oils 



Kind 


1895 


1900 


1902 


1903 


Crude 

Naphtha .... 
Illuminating . . 
Lubricating and 

Paraffin . . . 
Residuum . . . 


$5,161,710 

910,988 

34,706,844 

5,867,477 
13,063 


$7,340,749 

1,681,201 

54,692,872 

9,933,548 
845,337 


$6,331,011 

1,392,771 

49,079,055 

10,872,154 
922,152 


$6,782,136 

1,518,541 

51,355,668 

12,690,065 
282,129 


Total . . . 


$46,660,082 


$74,493,707 


$68,597,143 


$72,628,539 



The petroleums reach a wider market than any of our 
other exports, and over 38 per cent of the total quantity of 
crude oil produced is now exported in either crude or re- 
fined form. This was formerly sent away in cans, but it is 
now transported largely in bulk in tank steamers, some of 
which have a capacity of 60,000 barrels. (8 a) 

The following table gives the production of the different 
kinds of asphaltum for the last three years : — 

Production of Asphaltum in the United States from 1901-1903 





1901 


1902 


1903 


Variety 


Short 
Tons 


Value 


Short 
Tons 


Value 


Short 
Tons 


Value 


Bituminous sandstone 
Bituminous limestone 

Mastic 

Hard and refined or 

gum 

Liquid or maltha . . 


34,248 
6,970 

19,316 
2,600 


$138,601 
33,375 

333,509 
49,850 


57,837 
2,869 

22,321 

1,605 


$156,993 
19,817 

264,817 
20,172 


38,633 

2,520 

961 

12,896 

58 


$118,001 

8,800 

11,532 

343,799 
1,150 



PETROLEUM, NATURAL GAS, OTHER HYDROCARBONS Q5 

The production by states in 1903 was as follows : — 



State 

California . . . . 

Texas 

Utah 

Kentucky .... 
Indian Territory . . 
Arkansas 



Quantity 
Short Tons 


Value 


74,578 


$702,758 


2,158 


30,550 


5,619 


188,357 


12,578 


50,163 


5,107 


28,150 


1,215 


5,468 



Since deposits of the purer type, such as lake asphalt, 
are very scarce in the United States, the supply for domes- 
tic consumption is obtained from foreign countries. The 
imports for the last two years are given below : — 

Imports of Asphaltum 





1902 


1903 




Long Tons 


Value 


Long Tons 


Value 


West Indies 

Venezuela 

All others 


106,844 

12,406 

375 


$ 358,316 

62,028 

8,533 


139,031 
16,445 
17,416 


$415,221 

74,874 
95,770 


Total 


119,625 


$428,877 


172,892 


$ 585,865 



The world's production for 1902 Avas as follows : — 
World's Production of Asphaltum in 1902 



Country 



Trinidad . . . 
United States . 
France . . . 
Italy .... 
Germany . . 
Austria-Hungary 
Spain .... 
Venezuela . . 



Short Tons 


Value 


178,230 


$ 828,347 


84,632 


461,799 


284,719 


390,254 


70,619 


151,829 


97,415 


146,470 


4,047 


67,623 


6,946 


12,356 


10,060 





66 ECONOMIC GEOLOGY OF THE UNITED STATES 



REFERENCES ON PETROLEUM 

Origin, Occurrence, and Technology. 1. Folger, Ann. Rept. Secy, 
of Internal Affairs, 1892, Pt. Ill, p. B. (Petroleum production and 
products.) 2. Mineral Industry, II : 497, 1894. (Mining and Tech- 
nology.) 3. Newberry, Geol. Soc. Amer., Bull. 1 : 192, 1887. 4. Orton, 
Geol. Soc. Amer., Bull. IX: 85, 1892. (Origin and accumulation.) 
5. Orton, Kentucky Geol. Surv., 1894. (Origin.) 6. Peckham, 
Day, Maybery, etc., Proc. Amer. Phil. Soc, XXXVI: 93. (Origin 
and composition.) 7. Redwood, B., Treatise on Petroleum. (Ex- 
cellent.) London. 8. White, Geol. Soc. Amer., Bull. Ill: 187, 
1892. (Anticlinal theory.) 8 a. Oliphant, Mineral Census, 1902, 
Rept. on Mines and Quarries. (General and statistical.) 

Areal Reports. Alaska : 9. Martin, U. S. Geol. Surv., Bull. 225 : 365, 
1904. Also U. S. Geol. Surv., Bull. 259: 129, 1905. — California : 
10. Eldridge, U. S. Geol. Surv., Bull. 213 : 306, 1903. (General, 
good.) 11. Mabery and Hudson, Amer. Acad. Arts and Sci., Proc. 
XXVI: 255. (Composition.) 12. Watts, Bulls. Calif. State Min. 
Bureau, No. 3 (Central Valley), No. 11 (Los Angeles, Ventura, and 
Santa Barbara Cos.), No. 19 (General.) — Colorado: 13. Eldridge, 
Trans. Amer. Inst. Min. Engrs., XX: 442, 1892. (Florence field.) 
14. Fenneman, U. S. Geol. Surv., Bull. 225 : 383, 1904. (Boulder 
field.) 15. Fenneman, U. S. Geol. Surv., Bull. 260: 436, 1905. 
(Florence.) — Indiana : 16. Blatchley, Ind. Dept. Geol., 22d Ann. 
Rept. : 155, 1898. (Trenton limestone field.) 17. Chapters on 
petroleum in other annual reports of this series. 18. Orton, U. S. 
Geol. Surv., 8th Ann. Rept., II: 475, 1889. (Trenton limestone.) 
— Kansas: 19. Adams, U. S. Geol. Surv., Bull. 184, 1901. 20. Ha- 
worth, Kansas Geol. Surv., I: 232, 1896. (General.) 21. See also 
Volumes on Mineral Resources, issued by Kansas Geol. Surv. from 
1897 to 1901. — Kentucky: 22. Orton, Ky. Geol. Surv., 1894. (Gen- 
eral.) — Louisiana: 23. Hayes and Kennedy, U. S. Geol. Surv., Bull. 
212, 1903. (General.) — Michigan: 24. Gordon, Mich. Geol. Surv., 
Ann. Rept., 1901; 269, 1902. (Port Huron field.)— New York: 

25. Orton, N. Y. State Mus., Bull. 30, 1899. (General.) — Ohio : 

26. Bownocker, Ohio Geol. Surv., 4th Series, Bull. 1, 1903. 27. Gris- 
wold, U. S. Geol. Surv., Bull. 198. (Berea grit oil.) 28. Mabery, 
Amer. Chem. Jour. ; Dec, 1895. (Composition.) 29. Orton, Ohio 
Geol. Surv., VI : 60. 30. Orton, U. S. Geol. Surv., 8th Ann. Rept., 
II : 475, 1889. (Trenton limestone field.) — Pennsylvania : 31. Carll, 
Ann. Rept. Pa. Geol. Surv., 1885 ; I, 1886. 32. Reports I to IV of 
the same survey. — Texas: 33. Adams, U. S. Geol. Surv., Bull. 184, 
1901. (General.) 34. Hayes and Kennedy, U. S. Geol. Surv., Bull. 



PETROLEUM, NATURAL GAS, OTHER HYDROCARBONS 67 

212, 1903. 35. Phillips, Tex. Univ. Min. Surv., Bull. No. 1, 1900. 
(General.)— Washington: 36. Landes, Wash. Geol. Surv., I: 207. 
(General.) — West Virginia: 37. White, W. Va. Geol. Surv., la: 1, 
1904. (General.) 38. White, Geol. Soc. Amer., Bull. Ill: 1S7, 
1892. (Mannington field.) — Wyoming: 39. Knight and Slosson, 
Bull. 4, Wyo. School of Mines. (General.) 40. Bull. 3. (Crook 
and Uinta Cos.) 41. Bull. 5. (Newcastle field.) 42. Bull. 1. (Salt 
Creek field.) 

REFERENCES ON NATURAL GAS 

Ashburner. 43. Amer. Inst. Min. Engrs., Trans. XIY: 428. (Geology 
and Distribution in the United States.) 43 a. Orton, Geol. Soc. Amer., 
Bull. I: 87. (Rock pressure.) — California : 44. Watts, Calif. Min. 
Bureau, Bull. 3. (Central Valley.) — Indiana: 45. Phinney, U. S. 
Geol. Surv., 11th Ann. Kept., I: 589, 1891. 46. See also Ann. 
Repts. Ind. Geol. and Nat. Hist. Survey. — Kansas: 47. Adams, 
U. S. Geol. Surv., Bull. 184, 1901. 48. Haworth, Kan. Geol. Surv., 
I: 232, 1896. (General.) 49. Orton, Geol. Soc. Amer., Bull. X: 
99, 1899. (Iola field.) 50. Volumes on Mineral Resources, issued 
by Kan. Geol. Surv., 1897-1901. — New York: 51. Orton, N. Y. 
State Mus., Bull. 30, 1899. (General.) —Ohio: 52. Orton, Ohio 
Geol. Surv., XI. (General.) 53. Orton, U. S. Geol. Surv., 8th Ann. 
Kept., II: 475, 1889. — Pennsylvania: 54. Carll and Phillips, Ann. 
Rept. Pa. Geol. Surv., 1886, Pt. II, 1887. (General.) — Texas : 
55. Adams, U. S. Geol. Surv., Bull. 184, 1901. 

REFERENCES ON OIL SHALES 

55 a. Branner, Calif. Min. Bureau, Bull. 16. (Brazil.) 55 b. Carne, 
Memoirs, Dept. Mines and Agric, New South Wales, Geology No. 3. 
(General treatise.) 

REFERENCES ON ASPHALTUM 

General. 56. Dow, Min. Indus., X: 51, 1902. (History of Asphalt 
Industry.) 57. Greene, Amer. Inst. Min. Engrs., Trans. XVII: 355. 
(Uses.) — Origin: 58. Adams, Amer. Inst. Min. Engrs., Trans. 
XXXIII: 340, 1903. (Origin.) 59. Day, Eng. Record, XL: 347. 
60. Peckham, Amer. Phil. Soc, XXXVII: 108. (Genesis of 
bitumens.) — Special Papers: 61. Bailey and Ells, Geol. Surv.; 
Canada, 1876-77, 284. (Albertite.) 62. Blake, Amer. Inst. Min. 
Engrs., Trans. XVIII: 563. (Uintaite, Albertite, and Grahamite.) 
63. Coleman, Ontario Bur. Mines, 6th Ann. Rept., 159, 1897. 
(Anthraxolite.) — Areal : 64. Cooper, Calif. State Min. Bureau, 
Bull. 16. (California.) 65. Crosby, Amer. Naturalist, XIII: 229. 



68 ECONOMIC GEOLOGY OF THE UNITED STATES 

(Trinidad.) 66. Eldridge, U. S. Geol. Surv., 22d Ann. Rept., Ill : 
1902. (General occurrence in United States, excellent.) 67. Gos- 
ling, Sch. M. Quart., XVI : 41. (Ozokerite.) 68. Lane, Eng. and Min. 
Jour., LXXIII: 50. (Mich.) 69. Merivale, Eng. and Min. Jour., 
LXVI: 790, 1898. (Barbados.) 70. Parker, U. S. Geol. Surv., 
19th Ann. Kept., VI (ctd.) : 187, 1898. (Ozokerite.) Also Min. 
Ind., X: 50, 1902. 71. Peckham, Pop. Sci. Mo., LVIII: 225, 1901. 
(Trinidad and Venezuela.) 72. Phillips, Univ. of Tex. Miu. Surv., 
Bull. 3, 1902. (Texas.) 73. Vaughn, Eng. and Min. Jour., LXXIII: 
344. (Cuba.) 



CHAPTER III 
BUILDING STONES 

Under this term are included all stones for ordinary 
masonry construction, as well as for ornamentation, roofing, 
and flagging. The number of different kinds used is very 
great, and includes practically all varieties of igneous, sedi- 
mentary, and metamorphic rocks, but a few stand out 
prominently on account of their widespread occurrence 
and durability. 

The cost of a building stone naturally exerts decided in- 
fluence on its use. Since the ease of splitting and dressing 
a stone influences its cost, the texture is also of importance. 
Color is another factor in determining the value of a build- 
ing stone, and this, together with other considerations, some- 
times gets a fashion leading to the widespread use of certain 
stones. This has been well illustrated in the eastern cities 
of the United States where, for many years, Connecticut 
browstone was in such great demand for use in building 
private dwellings that much inferior stone was put on the 
market. More recently Indiana limestone and Ohio sand- 
stone have met the popular fancy, and these two are now 
used in vast quantities. 

Properties of Building Stones (1-6). — The following prop- 
erties have an important bearing on the value of a building 
stone : — 



70 ECONOMIC GEOLOGY OF THE UNITED STATES 

Color. — The color of rocks varies greatly, and those shown 
by common building stones include white, black, brown, 
red, yellow, and buff, while some are green, blue, or mottled. 
The color may vary in the same quarry. 

In igneous rocks the color may be that of the prevailing mineral, as 
in pink granite, where there is an excess of pink feldspar ; or it may be 
a composite due to the blending of the colors of several minerals, as in 
the case of ordinary gray granite, where the color results from the mix- 
ture of black mica and whitish quartz and feldspar. Sedimentary 
rocks commonly owe their color either to ferruginous cements, or to 
carbonaceous matter. The former give brown, yellow, red, or green 
colors depending on the condition of oxidation of the iron, while the 
latter produces gray, black, and bluish tints depending on the amount 
present. Sandstone and limestone free from either of these coloring 
agents are nearly if not quite white. 

Some stones change color on exposure to the air. For example, 
limestones or sandstones containing carbonaceous matter may bleach ; 
some black marbles fade to a white or gray ; and many red and green 
roofing slates, as well as many red granites, change color. Oxidation 
of evenly distributed pyrite may change gray or bluish-gray sandstones 
to buff color. If the minerals responsible for such change in color are 
not uniformly distributed, the stone assumes a blotchy appearance, but 
such changes are not necessarily an indication of deterioration. 

Texture. — Building stones vary in their texture from 
coarse-grained granites and conglomerates to fine-grained 
sandstones, limestones, and porplryries. 

Texture is an important property, for it influences both the dura- 
bility and the cost of stone. Other things being equal, a fine-grained 
rock is not only more durable, but splits better and dresses more evenly 
than a coarse-grained rock. Uneven texture, whether due to mineral 
grains or cement, is undesirable since it often causes uneven weathering. 

Density. — On the whole, dense stones resist weather bet- 
ter than porous ones, but there is great difference in the 
density of building stones. 



BUILDING STONES 71 

In general, though with some exceptions, igneous and metamorphic 
rocks have high density because of the close interlocking of the crystal- 
line grains. Sedimentary rocks of clastic origin, on the other hand, 
have less closely fitting grains, and unless the latter are very small, or 
the pores well filled with cement, they are apt to be porous. 

The specific gravity of a stone indicates its density ; and from the 
specific gravity the weight per cubic foot may often be approximately 
estimated by multiplying it by 62.5, the weight of an equal volume of 
water. While sufficiently accurate for very dense stones this method is 
liable to lead to incorrect results when applied to very porous rocks. 
Following are some average specific gravities of common building 
stones, as given by Hermann (1): granite, 2.65; syenite, 2.80; serpen- 
tine, 2.60; gneiss, 2.65; limestone, 2.60; dolomite, 2.80; sandstone, 
2.10; slate, 2.70. 

Hardness. — The hardness of a building stone is not neces- 
sarily dependent on the hardness of its component minerals, 
but is largely influenced by their state of aggregation. 

For example, a sandstone composed of quartz grains, but with little 
cementing material, may be so soft as to crumble easily in the fingers, 
while a limestone, whose grains of soft carbonate of lime fit closely and 
are firmly cemented, may be difficult to break with a hammer. The 
nature of the cement in sedimentary rocks, that is whether it is lime, 
silica, or iron, will also affect the hardness of the stone. Crystalline rocks 
owe their great hardness to the firm interlocking of the mineral grains. 

Strength. — Two kinds of strength, compressive and trans- 
verse, are to be considered in building stones. 

The compressive or crushing strength, which is expressed in pounds 
per square iuch, is the resistance which the rock offers to a crushing 
force, and is dependent chiefly on the size of the grains, state of aggrega- 
tion, and mineral composition. Because of the close interlocking of the 
grains of igneous rocks they are stronger than those of sedimentary 
origin, in which the strength is due chiefly to the cement which binds 
the grains together. Sedimentary rocks show greatest strength when 
dry, or when pressure is applied at right angles to the bedding. 



72 ECONOMIC GEOLOGY OF THE UNITED STATES 

Few building stones are subjected to pressures even approximately 
equal to their crushing strength. No domestic building stone at present 
used in the eastern market has a crushing strength of less than 6000 
pounds, yet the pressure even in the tallest buildings does not require 
a stone with a crushing strength exceeding 314.6 pounds, and this in- 
cludes the usual factor of safety of 20 per cent allowed by architects. 
Computations show that a stone at the base of the Washington monu- 
ment sustains a maximum pressure of 6292 pounds per square inch, 
which includes the usual factor of safety of twenty ; the crushing strength 
of the stone used in the base of the monument is however not less than 
10,000 to 12,000 pounds per square inch. 

The crushing strength of some soft limestones or sandstones may be 
but little above 3000 pounds per square inch, while that of diabase often 
exceeds 30,000 pounds per square inch. The accompanying table gives 
the crushing strength of a number of native stones. 

Crushing Strength of Building Stones 

Granite, Vinal Haven, Me 13,381 

Granite, East Saint Cloud, Minn. . . . 28,000 

Granite, Port Deposit, Md 19,750 

Dolomite marble, Tuckahoe, N.Y. . . . 13,076 

Limestone, Caen, France 3,550 

Sandstone, Portland, Conn 13,310 

Sandstone, E. Long Meadow, Mass. . . 8,812 

The published crushing tests of different stones cannot really be fairly 
compared because all have not been tested under exactly the same 
conditions. 

Transverse Strength. — The transverse strength is the load which a 
bar of stone, supported at both ends, is able to withstand without break- 
ing. It is measured in terms of the modulus of rupture, which represents 
the force necessary to break a bar of one square inch cross section, rest- 
ing on supports one inch apart, the load being applied in the middle. 
Although stones in buildings are rarely, if ever, crushed, they are fre- 
quently broken transversely, and therefore a knowledge of the transverse 
strength is of more importance than the crushing strength. A high 
crushing strength does not necessarily mean a high transverse strength. 
Unfortunately few stones have been tested in this manner. 



BUILDING STONES 78 

Porosity and Ratio of Absorption. — The porosity of build- 
ing stones varies widely. Most igneous rocks have little 
pore space and hence absorb little water ; but sedimentary 
rocks, especially sandstones, are often very porous. 

Many rocks, especially those of the sedimentary class, contain water 
in their pores when first quarried. This is known to quarrymen as 
quarry water, and it is present in some porous sandstones in sufficient 
quantities to interfere with quarrying during freezing weather. Mineral 
matter in solution in the quarry waters is deposited between the grains 
when the water evaporates, often in sufficient quantities to perceptibly 
harden the stone. 

Water is also present in the joint planes, and by its passage along 
these planes causes oxidation and rusting of the iron of the rock-forming 
minerals. This discolors the stone along and on either side of the joint 
planes, giving rise to a yellow color known as sap. 

Resistance to Frost. — Building stones show a varying 
degree of resistance to frost. 

Dense rocks, like granites, quartzites, and many limestones, and even 
some very porous rocks, are little affected ; but many porous and lami- 
nated rocks, like open sandstones and schists, disintegrate under frost 
action. This is due to the fact that moisture absorbed in the warmer 
weather, on freezing in the pores, expands, and either forces off small 
pieces or disrupts the stones. Since clay readily absorbs water, clayey 
rocks are sometimes similarly affected. 

Resistance to Heat. — All rocks expand when heated, and 
contract when cooled, but do not shrink down to their 
original dimensions. This permanent increase in size is 
termed permanent swelling, and though small when figured 
for one linear foot, is appreciable in long pieces. 

The following figures give the average of a number of tests of per- 
manent swelling in stone bars 20 inches long, heated from 32° F. to 
212° F., and then cooled to the original temperature: granite, .009 



74 ECONOMIC GEOLOGY OF THE UXITED STATES 

inches; marble, .009 inches; limestone and dolomites, .007 inches; 
sandstone, .0047 inches. 

The most severe test of a stone's resistance to rapid changes of 
temperature is to heat it to about 800° C. and then immerse it in cold 
water. Quartzites and hard sandstones withstand such treatment best ; 
some granites crack and crumble, and the carbonate rocks change to 
lime. 

Structural Features affecting Quarrying. — All rocks are traversed by 
planes of separation of one sort or another. In sedimentary rocks these 
consist of bedding and joint planes ; in igneous rocks, the latter alone 
are present ; and in metamorphic rocks, joint planes, a banding of 
minerals, and, very often, cleavage planes. 

Bedding Planes. — These may be either an advantage or a disadvan- 
tage to the quarryman. They are desirable because they facilitate the 
extraction of the stone ; but if numerous and closely spaced, the layers 
may be too thin for any purpose except nagging. They often serve 
as a means of entrance for the agents of weathering, and the stone 
may be disintegrated along the bedding planes while elsewhere fresh. 

Incipient planes of weakness, due either to the arrangement of 
minerals or to microscopic fractures in them, often give rise to planes 
of easy splitting which are of great value in quarrying, notably of 
granite. Such planes which permit splitting in approximately horizon- 
tal directions are called lift ; the most prominent vertical plane is called 
rift; and a less prominent vertical plane, approximately at right angles 
to the rift, is called the cut off. 

The position of the beds exerts an important influence on the cost 
of quarrying. When horizontal and of different quality, it may often 
be necessary to strip off worthless rock in order to reach the beds of 
good quality. In such cases, there is often less stripping to do in 
quarries opened on gently sloping ground. In regions of steep dip, it 
is sometimes possible to work the quarry as a cut, extracting the desired 
beds and leaving useless ones standing. 



BUILDING STONES 75 



GRANITES 



Characteristics of Granites (3). — As commonly used by 
quarrymen, the term granite includes all igneous rocks 
and gneiss ; but in this book it is used in the geological 
sense, which is more restricted. From the geological stand- 
point a granite is a noncrystalline, plutonic igneous rock 
consisting of quartz, orthoclase feldspar, and either mica 
or hornblende, or both. There are also varying but usually 
small quantities of other feldspars, and there may be sub- 
ordinate accessory minerals, such as pyrite, garnet, tourma- 
line, and epidote. 

Granites vary in texture from fine to coarse grained, and 
in some cases are porphyritic. They pass into gneisses by 
such insensible gradations that no sharp line can be drawn 
between the two. In color they vary, being, most com- 
monly, gray, mottled gray, red, pink, white, or green, 
according to the color or abundance of the component 
minerals. Most granites are permanent in their color, but 
some of bright red color bleach on exposure to weather. 

The average specific gravity of granites is 2.66, which corresponds 
to a weight of 166.5 pounds per cubic foot. They commonly contain 
less than 1 per cent of water, and often absorb two or three tenths 
more. Their crushing strength varies, but is apt to lie between 15,000 
and 30,000 pounds per square inch. 

Granites are among the most durable of building stones, but there 
is some variation in the durability of the different kinds. Other things 
being equal, fine-grained granites are more durable than coarse-grained, 
being less easily affected by changes of temperature. One of the 
most beautiful granites known, the Rapikivi granite of Finland, lacks 
in durability on this account. Pyrite and marcasite are injurious 
minerals, since they rust rapidly and may discolor the stone in an 



76 



ECONOMIC GEOLOGY OF THE UNITED STATES 



unsightly manner. Very few granites now in use show signs of decay ; 
but in those that do, the darker silicates are rusted, the luster of the 
feldspar is dulled, and, in some cases, the stone has begun to disinte- 
grate. Some red granites bleach on continued exposure to sunlight. 



Distribution of Granites in the United States ( 3 ) . — Granite 
usually occurs in great bosses frequently forming the cores 
of mountain chains. Removal of the overlying strata by 




Fig. 20. — Map showing distribution of crystalline rocks (mainly granites) in 
United States. After Merrill. Stone for Building and Decoration. 

denudation has revealed the granite, which, owing to its 
greater durability, is often left standing as peaks or domes 
by the farther removal of the surrounding, weaker . strata. 
Granites show a wide, geologic range, but most known 
occurrences are associated with the older formations. 

Granite forms an important source of durable building 
stone widely distributed in the United States (Fig. 20) ; 
but nearly 70 per cent of that quarried comes from the 



BUILDING STONES 77 

Atlantic states. There are several areas which will be 
briefly considered. 

Eastern Crystalline Belt (3, 8, 15, 21, 25, 32, 33). _ From 
northeastern Maine southwestward to eastern Alabama 
there is an important belt of granites and gneisses, mostly 
of pre-cambrian age. Those at the northeastern end of 
the belt, as far south as New York, are most extensively 
quarried, largely because of their peculiarly favorable loca- 
tion. In this belt those of Quincy, Massachusetts, Barre, 
Vermont, and Westerly, Rhode Island, are of value for 
monumental work. 

Central States. — In these states there are several widely 
separated areas : (1) the Minnesota- Wisconsin area (35), 
affording many fine stones ; (2) the southeastern Missouri 
area ; (3) east central Arkansas ; and (4) Llano County, 
Texas, all supplying stones of excellent quality. 

Western States. — There are many granite areas in the 
Cordilleras, including stone of various colors and texture ; 
but quarrying is almost entirely confined to California (12), 
Colorado (13), Montana, Washington (34), and Oregon for 
local use. The supply is inexhaustible. There is some 
quarrying, also, in the enormous mass of coarse-grained 
granite which forms the central portion of the Black Hills 
of South Dakota. 

Uses of Granite. — On account of its massive character 
and durability, granite is much employed for massive 
masonry construction, while some of the granites that take 
and preserve a high polish, and are susceptible of being 
carved, are in great demand for ornamental and monumen- 
tal work. Because of its greater durability, granite has 



78 ECONOMIC GEOLOGY OF THE UNITED STATES 

in recent years largely replaced marble for monumental 
purposes. 

The refuse of the quarries is often dressed for paving 
blocks or crushed for roads and railroad ballast. The size 
of the blocks which can be extracted from a granite quarry 
depends in part on the spacing of the joint planes, in part 
on the perfection of development of the rift, some of the 
monoliths that have been quarried being of immense size ; 
for example, one from Stony Creek, Connecticut, measured 
41 ft. x 6 in. x 6 in. ; one from Vinal Haven, Maine, 60 ft. 
X 5J ft. ; one from Barre, Vermont, 60 ft. x 7 ft. x 6 ft. 

Miscellaneous Igneous Rocks. — Other igneous rocks than granites 
are little used for structural work, though they are quarried in some 
localities. For example, the diabase, or trap, so abundant in the Tri- 
assic of the eastern states, is occasionally used for dimension blocks, 
but its chief value is for paving blocks and road metal. The basaltic 
rocks of the western states are often employed for similar purposes. 
Norites of great beauty occur in New York, and syenites of excellent 
quality have been quarried in Arkansas. Diorites are also quarried at 
scattered localities. Some of the porphyries and rhyolites of the Atlan- 
tic States possess considerable beauty when polished. A handsome 
porphyry is quarried in Wisconsin (35), and in the Cordilleran region 
both rhyolite and porphyry occur in numerous localities. A pink rhyo- 
lite and consolidated volcanic tuffs are used, to some extent, for 
building in Arizona. 

LIMESTONES AND MARBLES 

General Characteristics (!> 3 ). — A great series of sedi- 
mentary and metaniorphic rocks, composed chiefly of car- 
bonate of lime, or, in the case of dolomite, of carbonate of 
lime and magnesia, is included under the term limestone 
and marble. , These rocks also contain varying, but usually 
small amounts of iron oxide, iron carbonate, silica, clay, 



BUILDING STOKES 79 

and carbonaceous matter. When of metamorphic character, 
various silicates, such as mica, hornblende, and pyroxene, 
may be present. 

These calcareous rocks vary in texture from fine-grained, 
earthy, to coarse-textured, fossiliferous rocks, and from 
finely crystalline to coarsely crystalline varieties. There 
is, also, great range in color, the most common being blue, 
gray, white, and black, but beautiful shades of yellow, red, 
pink, and green, usually due to iron oxides, are also found. 
Their crushing strength commonly ranges from 10,000 
to 15,000 pounds per square inch, while their absorption is 
generally low. 

The mineral composition of limestone exerts a strong 
influence on its durability. Those limestones which are 
composed chiefly or wholly of carbonate of lime are liable 
to solution in waters containing carbon dioxide ; but dolo- 
mite limestones, especially coarse-grained ones, disintegrate 
rather than decompose. Streaks of mineral impurities cause 
the stone to weather unevenly. Pyrite is an especially inju- 
rious constituent, not only on account of its rusting, but 
also because the sulphuric acid set free by its decompo- 
sition attacks the stone. Black or gray limestones will 
sometimes bleach on exposure. 

Varieties of Limestones. — In the geological sense limestones are of 
sedimentary origin, while marbles are of metamorphic character, but 
in the trade the term marble is applied to any calcareous rock capable 
of taking a polish. In addition to the different varieties of marble 
and the ordinary limestones there are certain kinds of calcareous rock 
to which special names are given, as follows : — 

Dolomite, or dolomitic limestone, composed of carbonate of lime and 
magnesia, and to the eye alone often is indistinguishable from lime- 
stone. 



80 ECONOMIC GEOLOGY OF THE UNITED STATES 

Oolitic limestone, composed of small, rounded grains of concretionary 
character. 

Travertine, or calcareous tufa, a limestone deposited from springs. 
It is often sufficiently hard and durable for building, but rarely occurs 
in deposits of large size. 

Stalactitic and stalagmitic deposits, formed on the roofs and floors of 
caves, respectively, are often of crystalline texture and beautifully 
colored, and, when of sufficient solidity, are known as onyx marble. 

Fossiliferous limestones is a general term applied to those limestones 
which contain many fossil remains. Under this heading are included 
crinoidal limestone and coral-shell marble. Coquina is a loosely 
cemented shell aggregate, like that found near St. Augustine, Florida. 
Chalk is a fine, white, earthy limestone, composed chiefly of forami- 
niferal remains. 

Distribution of Limestones in the United States. — Lime- 
stones are found in many states, and in all geological for- 
mations from Cambrian to Tertiary, but those of the 
Paleozoic, which are much used in the Eastern and Central 
states, are more extensive and more massive than those of 
later formations. Although many large quarries have been 
opened to supply a local demand, the product is shipped 
to a distance from only a few localities. At present the 
sub-Carboniferous Bedford (18) oolitic limestone of Indiana 
(PI. VI) is, perhaps, the most widely used limestone in the 
United States. It occurs in massive beds from 20 to TO 
feet thick, and is said to underlie an area of more than 
70 square miles, Although soft and easily dressed, it has 
good strength, and has been used in many important cities 
of the United States. 

Cretaceous limestones are worked in Kansas, Nebraska, 
and Iowa, although the most important sources are in the 
Paleozoic formations. 



Plate VI 




BUILDING STONES 



81 



Distribution of Marbles in the United States (3) . — While 
some variegated marble is produced in the United States, 




Fig. 21. — Map showing marble areas of eastern United States. After Merrill. 
Stones for Building and Decoration. 

still most of those quarried are white, the greater part of 
the variegated stones being imported. The main supply 



82 ECONOMIC GEOLOGY OF THE UNITED STATES 

comes chiefly from regions of metamorphic rock, the eastern 
crystalline belt being the principal producer (Fig. 21). 
Vermont (32, 33) leads all other states in marble produc- 
tion, supplying 80 per cent of all the marble used for 
ornamental work in the country. The most important 
and largest quarries are those at Proctor (PI. VII) and 
West Rutland, where a thick and steeply dipping bed of 
marble occurs between other limestones. The marble bed, 
which has a thickness of 150 feet at the top of the quarry, 
narrowing to 75 feet at the bottom, is divisible into a 
series of well-marked layers of varying thickness, quality, 
and color, — white, blue, gray, and striped (33). Similar 
marbles are quarried in Massachusetts (3, 22), New York 
(3, 28), Maryland (21), and Georgia (15). 

A variegated red and white marble of some hardness is 
quarried at S wanton, Vermont (33), the brilliant red being 
caused by iron oxide, the white by calcite deposited in 
breccia cavities. 

The Trenton limestone in eastern Tennessee (3) supplies 
marbles of pinkish chocolate color with white variegation ; 
and certain layers are rendered peculiarly beautiful by the 
replacement of the fossils by calcite. It is used chiefly for 
interior decoration. 

Marble has been reported from various states west of the 
Mississippi, but as yet little quarrying has been done. That 
quarried in Inyo County, California, has attracted con- 
siderable attention in recent years. 

Most of the variegated marble used for interior decoration in this 
country is obtained from abroad, although ornamental stones of this 
class occur in the United States; however, up to the present time few 
attempts have been made to place them on the market. This may be 



Plate VII 




Marble quarry 
is vertical 
benches. 



Proctor, Vt. Photo., Vermont Marble Co. The banding of the rock 
The horizontal lines are caused by the stone being quarried in 



BUILDING STONES 83 

due to the fact that few quarrymen care to assume the temporary expense 
which their introduction might involve. 

Onyx Marbles (37-40). — Under this term are included two types of 
calcareous rock, one a hot-spring deposit, or travertine, formed at the 
surface, the other a cold-water deposit formed in limestone caves in 
the same manner as stalagmites and stalactites. Cave onyx is more 
coarsely crystalline and less transluscent than travertine onyx. The 
beautiful banding of onyx is due to the deposition of successive layers 
of carbonate of lime, while the colored cloudings and veinings are 
caused by the presence of metallic oxides, especially iron. 

Neither variety of onyx occurs in extensive beds, though both are 
widely distributed. Onyx is found in Arizona, California, and Colorado, 
but it has not been developed in any of these states except on a small 
scale. Most of the onyx used in the United States is obtained from 
Mexico, though small quantities are obtained from Egypt and north 
Algeria. 

The value of onyx varies considerably, the poorer grades selling for 
as little as 50 cents per cubic foot, while the higher grades bring $50 
or more. The earliest-worked deposits were probably those of Egypt, 
which were used by the ancients for the manufacture of ornamental 
articles and religious vessels; and the Romans obtained onyx from the 
quarries of northern Algeria. Many of the travertine onyx deposits 
occur in regions of recent volcanic activity, and all of the known 
occurrences are of recent geological age. 

SERPENTINE 

Pure serpentine is a hydrous silicate of magnesia; but beds of ser- 
pentine are rarely pure, usually containing varying quantities of such 
impurities, as iron oxides, pyrite, hornblende, and carbonates of lime 
and magnesia. The purer varieties are green or greenish yellow, while 
the impure types are various shades of black, red, or brown. Spotted 
green and white varieties are called ophiolite or ophicalite. 

Serpentine is sometimes found in sufficiently massive form for use in 
structural or decorative work; but, owing to the frequent and irregu- 
lar joints found in nearly all serpentine quarries, it is difficult to obtain 
other than small-sized slabs. Its softness and beautiful color have led 



84 ECONOMIC GEOLOGY OF THE UNITED STATES 

to its extensive use for interior decoration ; but since it weathers irregu- 
larly and loses luster, it is not adapted to exterior work. 

Though found in a number of states, most of the numerous attempts 
to quarry American serpentine have been unsuccessful. Considerable 
serpentine for ordinary structural work has been quarried in Chester 
County, Pennsylvania, and a variety known as Verdolite is worked 
near Easton, Pennsylvania. Quarrying operations are also under way 
in the state of Washington. 

SANDSTONES 

General Properties (1, 3). — While most sandstones are 
composed chiefly of quartz grains, some varieties contain 
an abundance of other minerals, such as mica, or, more 
rarely, feldspar, which in rare cases may even form the 
predominating mineral. Pyrite is occasionally present, and 
var}dng amounts of clay frequently occur between the 
grains, at times in sufficient quantity to materially influence 
the hardness and dressing qualities of the stone. The hard- 
ness of sandstones, however, usually depends on the amount 
and character of the cement, varying from those having 
so small an amount of silica or iron oxide cement that 
the stone crumbles in the fingers to those quartzites whose 
grains are so firmly bound by silica that the rock resembles 
solid quartz. With these differences the chemical compo- 
sition varies from nearly pure silica to sandstone with a 
large percentage of other compounds. (For analyses, see 
Kemp's "Handbook of Rocks.") 

There are many colors among sandstones, but light gray, 
white, brown, buff, bluish gray, red, and yellow are most com- 
mon. In density sandstones range from the nearly imper- 
vious quartzites to the porous sandrocks of recent geologic 
formations, and consequently they show a variable absorption. 



BUILDING STONES 85 

Most sandstones contain some quarry water, and those with 
appreciable amounts are softer and more easy to dress when 
first quarried ; but they cannot be quarried in freezing 
weather. The average specific gravity of sandstone is 2.3, 
and accordingly a cubic foot weighs about 140 to 150 pounds. 
On the whole, sandstones resist heat well and are usually 
of excellent durability, since they contain few minerals that 
easily decompose. When they disintegrate it is commonly 
by frost action. The injurious minerals are pyrite, mica, 
and clay. Pyrite is likely to cause discoloration on weather- 
ing ; the presence of mica tends to cause the stone to scale 
off if set on edge ; and clay may cause injury to the stone in 
freezing weather on account of its capacity for absorbing 
moisture. The value of a sandstone is often lessened by 
careless quarrying, or by placing it on edge in the building, 
thus exposing the bedding planes to the entrance of water. 

Varieties of Sandstone. — With an increase in the size of 
their grains, sandstones pass into conglomerates on the one 
hand and with an increase in clay into shales. By an in- 
crease in the percentage of carbonate of lime they may also 
grade into limestones. 

On account of these variations, as well as the difference in color and 
the character of the cement, a number of varieties of sandstone are 
recognized, of which the following are of economic value : arkose, a 
sandstone composed chiefly of feldspar grains ; Jlagstone, a thinly bedded, 
argillaceous sandstone used chiefly for paving purposes ; Milestone, a flag- 
stone much quarried in New York ; freestone, a sandstone which splits 
freely and dresses easily; broionstone, a term formerly applied to sand- 
stones of brown color, obtained from the eastern Triassic belt, and since 
stones of other colors are now found in the same formation, the term 
has come to have a geographic meaning and no longer refers to any 
specific physical character. 



86 ECONOMIC GEOLOGY OF THE UNITED STATES 

Distribution of Sandstones in the United States. — Sand- 
stones occur in all formations from pre-Cambrian to Ter- 
tiary. They are so widely distributed that for local supply 
there are numerous small quarries in many states, but there 
are several areas which have been operated on an extensive 
scale, some of them for many years. Of these, one of the 
best known is the Triassic Brownstone belt, which extends 
from the Connecticut Valley in Massachusetts southwest- 
ward into North Carolina. 

Among the Paleozoic strata there are many sandstones, 
often massive, and usually dense and hard. Of these the 
Medina and Potsdam are specially important and much 
quarried in New York State (27, 28). The same forma- 
tions extend southward along the Appalachians and are 
available at several points. Devonian flagstones are ex- 
tensively quarried at several localities in New York and 
Pennsylvania. At the present time the Lower Carbon- 
iferous Berea sandstone of Ohio (29) is in great demand 
because of its light color, even texture, and the ease with 
which it is worked. Moreover, it has the peculiar property 
of changing to a uniform buff on exposure to the air. There 
are numerous other Paleozoic sandstones in the central 
states, among them the Potsdam which covers a wide area 
in Michigan and Wisconsin (35). Some of this stone is 
bright red in color. 

The Mesozoic and Tertiary strata of the West contain an 
abundance of sandstone strata, and quarries opened in many 
of them yield a good quality of stone. Though usually less 
dense and hard than the Paleozoic sandstones, they serve 
admirably for buildings in the mild or dry climates of the 
West. 



BUILDING STONES 



87 



Uses of Sandstones. — The wide distribution of sandstones 
makes them an important source of local structural material. 
They are chiefly used for ordinary building work, and but 
little for massive masonry or monuments. The thin-bedded 
flagstones are much used for flagging, and some of the 
harder sandstones are split up for paving blocks. For other 
uses, see Abrasives. 



SLATES 

General Characteristics (3, 26). — Slates are metamorphic 
rocks derived from clay or shale or more rarely from igneous 
rocks (11). Their value depends upon the presence of a 
well-defined plane of splitting, called cleavage (Fig. 22), de- 
veloped by metamorphism through the rearrangement and 
flattening of the original 
mineral grains and the 
development of mica- 
ceous minerals. The 
cleavage usually de- 
velops at a variable 
angle to the bedding 
planes which are often 
completely obliterated by the metamorphism. When not 
completely destroyed the bedding planes are marked by 
parallel bands, called ribbons, cutting across the planes of 
cleavage, but so perfect is the cleavage in the best slates that 
the rock readily splits into thin sheets with a smooth surface. 

Slates are commonly so fine grained that the mineral com- 
position is not evident to the eye, but the microscope re- 
veals the presence of many of the varied mineral grains 
found in shale, and in addition much chlorite, developed by 




QUARRY FLOOR 



Fig. 22. — Section showing cleavage and bed- 
ding in slate. After Dale, U. S. Geol. Surv., 
19t?i Ann. Rept.] III. 



88 



ECONOMIC GEOLOGY OF THE UNITED STATES 






metamorphism. Owing to the presence of carbonaceous 
particles, most slates are black or bluish black, but green, 

purple, and red slates are also 
known. The specific gravity of 
slate is about 2.7, and a cubic 
foot weighs between 170 and 175 
pounds. 

Most slates are fairly durable, 
though the presence of pyrite 
I ~ I TT along" the . ribbons may lead to 

Fig. 23. — Section in slate quarry ° J 

their decay. Some colored slates 
fade on exposure to the weather, 

e and/, green; g and h, gray . i • i • i 

green ; i.quartzite;.;, gray with but this change, which IS due to 

black patches. After Dale. the bleaching of certain minera l 

grains, does not necessarily result in loss of strength or 
disintegration. 




with cleavage parallel to bed- 
ding, a, purple slate ; b, un- 
worked ; c and d, variegated : 



Distribution of Slates in the United States. — Since slates 
are of metamorphic origin, they are limited to those regions 
in which the rocks are metamorphosed, and at present the 
greater part of our supply comes from the Cambrian and 
Silurian strata of the eastern crystalline belt of the Atlantic 
states. 

A series of quarries producing red, green, purple, and 
variegated slates are located in a belt of Cambrian and 
Hudson River strata along the border of New York (PI. 
VIII) and Vermont (26,33). 

Black slates are quarried in Maine (3), New Jersey (3), 
Pennsylvania (3), Maryland (21), Georgia (3), and Virginia 
(3). Other producing states are Minnesota, California (11), 
and Arkansas (9). 



Plate VIII 




View of green-slate quarry, Pawlet, Vt. Photo, by H. Ries. 



BUILDING STOXES 



89 



Uses of Slate. — Slate is best known as a roofing material, 
but it is also used for mantels, billiard-table tops, floor tiles, 
steps, flagging, slate pencils, acid towers, wash tubs, etc. 
The process of marbleizing slates for mantels and fireplaces 
is carried on at several localities. 

In quarrying slate there is from 40 to 60 per cent waste, 
which is greater than in any other building stone; but the 
introduction of channeling machines in quarrying has done 
much to reduce this. The discovery of a use for this waste 
has been an important problem, which has thus far been only 
partially solved. It is sometimes ground for paint, and 
attempts have been made to utilize it in the manufacture 
of bricks and Portland cement. 

Production of Building Stones. — The production of build- 
ing stones by kinds for several years was as follows : — 





Production of Building Stones 
United States 


IN THE 




1900 


1901 


1908 


1903 


Granite and Trap . 
Marble .... 

Slate 

Sandstone and 

Bluestone . . . 
Limestone . . . 


$12,675,617 
4,267,253 

4,240,466 

6.471.384 
16,666,625* 


$15,976,961 
1,965,699 

4,7S7..V_ ) ;> 

8,138,680 
21.747,0611 


•^ 18,257,944 
5,044,182 

5,696,051 

10,601,171 
24,959,751 » 


118,436,087 
5,362,686 
6,256,885 

11,262,259 

26,642.551 » 


Total .... 


44,321,345 


55,615,926 


64.559,099 


67,960,468 



The value of the building stones produced by the several 
more important states, together with the kind of stone pro- 
duced chiefly in 1903, is given below. 

1 Does not include limestone used as flux. 



90 



ECONOMIC GEOLOGY OF THE UNITED STATES 





Production of Building Stones in More 




Important States in 1903 




Total Value 


Kind produced Chiefly 


Pennsylvania . . 


$12,589,202 


Limestone 


Vermont . . 






5,889,208 


Marble 


Maine . . . 






3,611,140 


Granite 


Ohio . . . 






5,280,472 


Limestone 


New York . 






5,182,850 


Limestone 


Massachusetts 






4,443,601 


Granite 


Indiana . . 






2,903,284 


Limestone 


Georgia . . 






1,577,134 


Granite 


Maryland 






1,344,722 


Granite 


All others 






42,821,613 





In 1903 the slate exported was valued at 1628,612. 



REFERENCES ON BUILDING STONES 

General on Properties. 1. Hermann, Steinbruchindustrie und Stein- 
bruchgeologie, Berlin, 1899. Borntrager Bros. 2. Merrill, Min- 
eral Census, 1902. (Mines and Quarries.) 3. Merrill, Stones for 
Building and Decoration, 3d ed., New York, 1904. Wiley & Sons. 
For general information on properties and testing see also, 4. Buck- 
ley, Jour. Geol., VIII : 160 and 333, 1900. 5. Julien, Amer. 
Geologist, XXI : 397, 1898. 6. Merrill, Maryland Geol. Surv., II : 
47, 1898. 7. Watson, Ga. Geol. Surv., Bull. 9-A, 1903. 

Areal Reports. Alabama : 8. Smith, Eng. and Min. Jour., LXVI : 398. 
(General.)— Arkansas: 9. Dale, U. S. Geol. Surv., Bull. 225: 414, 
1904. (Slate.) 10. Hopkins, Ark. Geol. Surv., Ann. Kept., 1890; 
IV, 1893. (Marbles.) — California : 11. Eckel, U. S. Geol. Surv., 
Bull. 225 : 417, 1904. (Slate.) 12. Jackson, Calif. State Min. Bureau; 
8th Ann. Rept. : 885, 1888. (General.) — Colorado : 13. Lakes, 
Mines and Minerals, XXII : 29 and 62, 1901. (General.) — 14. 
Merrill, Stones for Building and Decoration, New York, 1904. 
— Georgia: 15. McCallie, Ga. Geol. Surv., Bull. 1, 1894. (Marbles.) 
16. Watson, Ibid., Bull. 9-A, 1903. (Granites and Gneisses.) — 
Indiana: 17. Hopkins, Ind. Geol. and Nat. Hist. Surv., 20th Ann. 
Rept. : 188, 1896. 18. Siebenthal, U. S. Geol. Surv., 19th Ann. Rept., 
VI : 292, 1898. (Bedford limestone.) 19. Thompson, Ind. Geol. and 
Nat. Hist. Surv., 17th Rept.: 19, 1891. (General.) —Maine : 20. 



BUILDING STONES 91 

Merrill, Stones for Building and Decoration. Wiley and Sons, New 
York, 1904. — Maryland: 21. Matthews, Md. Geol. Surv., 11:125, 
1898. (General.) — Massachusetts: 22. Whittle, Eng. and- Min. 
Jour., LXVI : 336, 1898. (General.) — Michigan : 23. Benedict, 
Stone, XVII : 153, 1898. (Bayport district.) — Missouri : 24. Buck- 
ley and Buehler, Mo. Bur. Geol. and Mines, Bull. 2, 1904. — New 
Hampshire: 25. Hitchcock, 10th Census U. S., X : 124, 1884. — New 
York: 26. Dale, U. S. Geol. Surv., 19th Ann. Kept., Ill : 153, 1899. 
(Slate belt.) 27. Dickinson, X. Y. State Museum, Bull. 61, 1903. 
(Bluestone and other Devonian sandstones.) 28. Smock, X. Y. 
State Museum, Bull. 3, 1888. — Ohio: 29. Orton, Ohio Geol. Surv., 
V : 578, 1884. (General.) —Pennsylvania : 30. Hopkins, Penn. 
State College, Ann. Rept., 1895 ; Appendix, 1897. (Brownstones.) 
31. Lesley, Tenth Census, U. S., X : 146, 1884. (General.) — 
31a. South Dakota: Todd, S. Dak. Geol. Surv., Bull. 3 : 81, 1902. 
(General.) — Vermont: 32. Perkins, Rept. of State Geologist on 
Mineral Industries of Vt., 1899-1900, 1900, 1903-1904; and 33. Re- 
port on Marble, Slate, and Granite Industries, 1898. — Washington: 

34. Shedd, Wash. Geol. Surv., II : 3, 1902. (General.) —Wisconsin : 

35. Buckley, Wis. Geol. and Nat. Hist. Surv., Bull. IV, 1898. 
(General.) — Wyoming: 36. Knight, Eng. and Min. Jour., LXVI: 
546, 1898. 

REFERENCES ON ONYX MARBLE 

37. DeKalb, "Onyx Marbles," Trans., Am. Inst. Min. Engrs., XXV: 
557, 1896. 38. Merrill, Stones for Building and Decoration (^New 
York), 3d ed., 1904. 39. Merrill, Ann. Rept. U. S. Xat. Mus. 
(Washington), 1894. 40. Merrill, Min. Indus., Vol. II, "Onyx," 
1894. 



CHAPTER IV 

CLAY 

Definition. — Clay, which is one of the most widely dis- 
tributed materials and one of the most valuable commercially, 
may be defined as a fine-grained mixture of the mineral kao- 
linite (the hydrated aluminum silicate) with fragments of 
other minerals, such as silicates, oxides, and hydrates, and 
also often organic compounds (sometimes classed as col- 
loids), the mass possessing plasticity when wet and becom- 
ing rock hard when burned to at least a temperature of 
redness. 

Residual Clays (42). — Clays are derived primarily and 
principally from the decomposition of crystalline rocks, 
more especially feldspathic varieties, and deposits thus 
formed will be found overlying the parent rock and grad- 
ing down into it. From its method of origin and position 
it is termed a residual clay (Fig. 24). 

All residual clays show a variable amount of kaolinite or clay-substance. 
This mineral, which is white in color, results from the decomposition 
of feldspar, either by weathering, or, less often, by the action of volcanic 
vapors. The decay of a large mass of pure feldspar would therefore 
yield a mass of white clay, but in most instances, the feldspar is asso- 
ciated with other minerals, such as quartz, mica, and hornblende, all 
of which, except the quartz, decay with the greater or less rapidity, 
and some of these, such as the hornblende, may likewise yield a 
hydrous aluminum silicate. Any ferruginous minerals in the rock will, 
in decomposing, form limonite, which stains the mass. 

92 



CLAY 



93 




Large masses of pure feldspar are rare, but feldspathic rocks, such 
as granite or syenite, are more common, and these will also decompose 
to clay ; but, since the parent rock contains other minerals, such as 
quartz or mica, these 
will either remain as 
sand grains in the 
clay, or, by decom- 
position, will form 
soluble compounds, 
or iron stains. The 
decay of many rocks, 
for example, lime- 
stone and shale, in 
addition to the crys- 
talline rocks, produces a residuum of clay. Kaolin is a white-burning 
residual clay, but it is rare. 

The extent of a deposit of residual clay will depend on the extent 
of the parent rock and the topography of the land, which also influences 
its thickness. On steep slopes much of the clay may be washed away 
and residual clays are also rare in glaciated regions, for the reason that 
they have been swept away by the ice erosion. They are consequently 
wanting in most of the Northern states, but abundant in many parts 
of the Southern states, where the older formations appear at the surface. 

Sedimentary Clays (42). — With the erosion of the land 
surface the particles of residual clay become swept away 

to lakes, seas, or 



Fig. 24. — Section showing formation of residual clay. 
After Pies, U. S. Geol. Surv., Prof. Paper, 11:16. 



LOAMY CLAY 

CLAY 

SAND 

SAND AND GRAVEL 



the ocean, where 
they settle down 
in the quiet water 
as a fine alumin- 
ous sediment, 
forming a deposit 
of sedimentary 
clay (Fig. 25). Such beds are often of great thickness and 



Fig. 25. — Section of a sedimentary clay deposit. After 
Ries, U. S. Geol. Surv., Prof. Paper, 11:18. 



94 ECONOMIC GEOLOGY OF THE UNITED STATES 

vast extent. With the accumulation of many feet of other 
sediments on top of them, they often become solidated either 
by pressure or by the deposit of a cement around the grains. 
Consolidated clay is termed shale, and this upon being ground 
and mixed with water often becomes as plastic as an uncon- 
solidated clay. 

Sedimentary clays may be divided into the following 
groups according to their mode of origin and form of 
deposit. 

Marine Cloys. — Formed by the deposition on the ocean floor of 
the finer particles derived from the waste of the land. Such ancient 
sea-bottom clays have been elevated to form dry land in all the con- 
tinents, in many cases forming consolidated clay strata, but elsewhere, 
especially in coastal plains, in unconsolidated condition. Extensive 
clay deposits are also formed in protected estuaries and lagoons along 
the sea coast. 

Flood-plain Clays. — Formed by the deposition of clayey sediment 
on the lowlands bordering a river during periods of flood. Layer 
upon layer, this deposit builds a flood plain often of great extent 
and depth. Such areas of flood-plain clays are most extensive along 
the greater rivers and in the deltas which they have built in the 
sea. 

Lake Clays. — Clay is deposited on the bottom of many lakes and 
ponds in the same manner as on the ocean bottom. Where the 
streams bring only fine particles the filling of a lake may be entirely 
of clay. Many lakes have been either drained or completely filled 
and their clays therefore made available. This is especially true of 
small, shallow lakes formed during the Glacial Period. 

Glacial Clays, commonly known as till or bowlder clay, a rock flour 
ground in the glacial mill in which rock fragments were worn down to 
clay by being rubbed together or against the bed rock over which the 
ice moved. When the ice melted, this deposit was left in a sheet of 
varying thickness and characteristics over a large part of the area 
which the ice covered. 



CLAY 95 

JEolian Clays. — Wind drifts drive clay about, and in favorable posi- 
tions causes its accumulation in beds. This is true of the Chinese loess, 
a wind-blown deposit derived from residual soils and drifted about in 
the arid climate of interior China. Some at least of the loess clays of 
the Mississippi Valley seem to have a similar origin, the source of the 
clay being glacial deposits ; in other cases loess seems to be a water 
deposit either in shallow lakes or else in broad, slowly moving 
streams. 

Properties of Clay. — These are of two kinds, physical 
and chemical, and since they exercise an important influence 
on the behavior of the clay, the most important ones may 
be described. 

Chemical Properties (42). — The number of common ele- 
ments which have been found in clays is great, and . even 
some of the rarer ones have been noted ; but in a given 
clay the number of elements present is usually small, being 
commonly confined to those determined in the ordinary 
chemical analysis, which shows their existence in the clay, 
but not always the state of the chemical combination. 
The common constituents of a clay are silica, alumina, 
ferric or ferrous oxide, lime, magnesia, alkalies, titanic acid, 
and combined water. Organic matter, though often pres- 
ent, is usually in small amounts, and carbon dioxide is 
always found in calcareous clays. The effect of these 
may be noted briefly. 

Silica is most often present in the form of quartz grains ; but it 
may also be contained in grains of undecomposed minerals. It aids 
in lowering the plasticity and shrinkage, and helps to increase the 
refractoriness at low temperatures. A clay high in silica (70 to 80 
per cent) is usually sandy. Alumina, which is most abundant in white 
clays, is a refractory ingredient. Iron oxide acts as a coloring agent in 
both the raw and burned clay, small quantities coloring a burned clay 



9Q ECONOMIC GEOLOGY OF THE UNITED STATES 

buff, and larger amounts (4 to 7 per cent), if evenly distributed, turning 
it red. It also acts as a flux in burning. Whatever the iron compound 
present in the raw clay it changes to the oxide in burning. Lime, 
magnesia, and alkalies are also fluxing ingredients of the clay. The 
combined percentage of fluxing impurities is small in a refractory clay, 
and often high in a low grade one. Lime, if present in considerable 
excess over the iron, will, in burning, exert a bleaching effect on the 
iron. For this reason, highly calcareous clays, such as those in the 
Great Lake region, burn cream or buff. When lime is present in large 
amounts it also causes clay to soften more rapidly in firing than it 
otherwise would. 

Chemically combined water and organic matter both pass off at a 
temperature of very dull redness (450° to 650° C). Their loss leaves 
the clay temporarily porous until fire shrinkage sets in. Titanic acid, 
though rarely exceeding 1 per cent, acts as a flux at high tempera- 
tures at least. Sulphur trioxide is rarely present in sufficiently high 
amounts to interfere with the successful burning of the clay. 

Physical Properties (42). — These include plasticity, ten- 
sile strength, air and fire shrinkage, fusibility, and specific 
gravity. 

Plasticity may be defined as the property which clay possesses of 
forming a plastic mass when mixed with water, thus permitting it to be 
molded into any desired shape, which it retains when dry. This is an 
exceedingly important character of clay. Clays vary from exceedingly 
plastic, or " fat " ones, to those of low plasticity which are " lean " and 
sandy. Plasticity is probably due in part to fineness of grain, and in 
part to the presence of colloids. 

Tensile strength is the resistance which a mass of air-dried clay offers 
to rupture, and is probably due to interlocking of the particles. Tests 
show that the tensile strength of clays varies from 15 to 20 pounds per 
square inch up to 400 pounds or more per square inch. Many common 
brick clays range from 100 to 200 pounds. 

Shrinkage is of two kinds — air shrinkage and fire shrinkage. The 
former takes place while the clay is drying after being molded, and is 



CLAY 97 

due to the evaporation of the water, and the drawing together of the 
clay particles. The latter occurs during tiring, and is due to a com- 
pacting of the mass as the particles soften under heat. Both are 
variable. In the manufacture of most clay products an average total 
shrinkage of about 8 or 9 per cent is commonly desired. Excessive air or 
fire shrinkage causes cracking or warping of the clay. To prevent this 
a mixture of clays is often used. 

Fusibility is one of the most important properties of clays. When 
subjected to a rising temperature, clays, unlike metals, soften slowly, and 
hence fusion takes place gradually. In fusing, the clay passes through 
three stages, termed, respectively, incipient fusion, vitrification, and 
viscosity. 

In the lower grades of clay, that is, those having a high percentage 
of fluxing impurities, incipient fusion may occur at about 1000° C, 
while in refractory clays, which are low in fluxing impurities, it may 
not occur until 1300° or 1400° C. is reached. The temperature interval 
between incipient fusion and vitrification may be as low as 30° C. in 
calcareous clays, or as much as 200° C. in some others. The recognition 
of this variation is of considerable practical importance, and vitrified 
products, such as paving bricks and stoneware, have to be made from 
a clay in which the three stages of fusion are separated by a dis- 
tinct temperature interval. The importance of this rests on the fact 
that it is impossible to control the temperature of a large kiln with- 
in a few degrees, and there must be no danger of running into a 
condition of viscosity in case the clay is heated beyond its point of 
vitrification. 

Specific gravity varies commonly from about 1.70 to 2.30. 

Chemical Composition. — As might be expected from their 
diverse modes of origin, clays vary widely in their chemical 
composition. There is every gradation from those which, 
in composition, closely resemble the mineral kaolinite to 
those, like ordinary brick clays, in which there is a high 
percentage of impurities. This variation is shown in the 
following table : — 



ECONOMIC GEOLOGY OF THE UNITED STATES 



















< 


i< 


< 












->-3 






i-s 




j i^ 








1 

g 
13 
o 

•4 




§6 

P* fa 

w fa 
►J « 


5* 

as 

fa M 

,1^ 


•< 

3«2 


M H 

fa a 

S«2 


Q O 

sS 

II 


K 
PS 
H 

so 


P H 


P. 

cq h 

SI a 


iTE" 

5S 




M 


w 


M 


fa 


fa 


fa 


02 


Hi 


"U 


o 


pq 


Si0 2 


46.3 


62.4 


45.7 


61.6 


52.52 


59.92 


67.84 


68.62 


67.78 


38.07 


54.64 


A1 2 3 


39.8 


26.51 


40.61 


28.38 


31.40 


27.56 


21.83 


14.98 


16.29 


9.46 


14.62 


Fe 2 3 


— 


1.14 


1.39 


.52 


2.34 


1.03 


1.57 


4.16 


4.57 


2.70 


5.69 


CaO 


— 


.57 


.45 


.46 


.4 


tr. 


.28 


1.48 


.6 


15.84 


5.16 


MgO 


— 


.01 


.09 


.36 


.42 


tr. 


.24 


1.09 


.727 


8.5 


2.90 


K 2 


— 


.98 


2.82 


— 


} - 


.64 


2.24 


3.36 


2.001 


2.76 


5.89 


Na 2 


— 






— 














H 2 

Moist 


13.9 


8.8 
.25 


8.98 
.35 


5.08 


\ 12.42 


/9.70 

U.12 


5.90 

.80 


3.55 

2.78 


} 6.24 


2.49 


3.74 

.85 










Ti0 2 


Ti0 2 






MnO 


Ti0 2 


C0 2 


C0 2 










3.6 


.96 






.64 


.78 


20.46 


4.80 
MnO 

.76 



Classification of Clay. — It is possible to base a classifica- 
tion of clays either on origin, chemical and physical proper- 
ties, or uses. But since the subdivisions which can be made 
are not sufficiently distinct, each of these gives rise to a more 
or less unsatisfactory grouping. The following classifica- 
tion is based partly on mode of origin and partly on physical 
characters : — 

1. Residual clays. 

A. White-burning (kaolins, formed from feldspathic rocks). 

B. Colored-burning (formed from igneous, metamorphic, and 

many sedimentary rocks). 

2. Clastic, or mechanically formed clays. 

A. Water formed (of variable extent, depending on locality and 
mode of deposit). 

a. White-burning (ball and paper clays). 

b. Colored-burning (brick and pottery clays). 



CLAY 99 

B. Glacial clays (often stony; all colored-burning). 

C. Wind-formed clays (some loess). 

3. Chemical precipitates (some flint clays). 

Kinds of Clays. — Many kinds of clays are known by 
special names, the more important of which are the 
following : — 

Adobe. A sandy, often calcareous, clay used in the west and south- 
west for making sun-dried brick. Ball clay. A white-burning, plastic, 
sedimentary clay, employed by potters to give plasticity to their mixture. 
Brick clay. Any common clay suitable for making ordinary brick. 
China clay. A term applied to kaolin (q.v.). Earthenware clay. Clay 
suitable for the manufacture of common earthenware, such as flower 
pots. Fire clay. A clay capable of resisting a high degree of heat. 
Flint clay. A peculiar flintlike, fire clay, which when ground up and 
wet develops no plasticity. Chemically it differs but little, if at all, 
from the plastic fire clays. Moreover, the two often occur in the same 
bed, either in separate layers or irregularly mixed. Gumbo. A very 
sticky, highly plastic clay, occurring in the central states, and used for 
making burned-clay ballast (1). Kaolin. A white-burning residual 
clay, employed chiefly in manufacture of white earthenware and por- 
celain. Loess. A sandy, calcareous, fine-grained clay, covering thou- 
sands of square miles in the Central states, and of wide use in brick 
making. Paper clay. Any fine-grained clay, of proper color, that can 
be employed in the manufacture of paper. Pipe clay. A loosely used 
term applied to any smooth plastic clay. Strictly speaking, it refers to 
a clay suited to the manufacture of sewer pipe. Pottery clay. Any 
clay suitable for the manufacture of pottery. Retort clay. A plastic 
fire clay, used in making gas retorts. The term is a local one used 
chiefly in New Jersey. Sagger clay. A loose term applied to clays 
employed in making saggers ; they are of value for other purposes as 
well. Stoneware clay. A very plastic clay, which burns to a vitrified 
or stoneware body. Terra-cotta clay. Clay suitable for the manufac- 
ture of terra cotta. The term has no special significance, as a wide 
variety of clays are adapted to this purpose. 

LQFQ, 



100 ECONOMIC GEOLOGY OF THE UNITED STATES 

Geological Distribution. — Clays have a wider distribution 
than most other economic minerals or rocks, being found in 
all formations from the oldest to the youngest. The pre- 
Cambrian crystallines yield both white and colored residual 
clays, usually the result of weathering, though more rarely of 
solfataric action. In the Paleozoic rocks, deposits of shale, 
and sometimes of clay, are found in many localities ; and, 
since they are usually marine sediments, the beds are often 
of great extent and thickness. With the exception of cer- 
tain Carboniferous deposits, the Paleozoic clays are mostly 
impure. The Mesozoic formations contain large supplies of 
clays and shale suitable for the manufacture of bricks, terra 
cotta, stoneware, fire brick, etc. 

The Pleistocene clays are all surface deposits, usually 
impure, and individually of limited extent, although they 
are thickly scattered all over the United States. Their 
chief value is for brick and tile making. They have been 
accumulated by glacial action, on flood plains, in deltas, or 
in estuaries and lakes. 

Distribution of Clays by Kinds. — Kaolins (59). — Since 
kaolins are derived only from crystalline or igneous rocks, 
their distribution is limited ; indeed, at present the only 
deposits worked are in the eastern states. Being com- 
monly formed by the weathering of pegmatite veins, kaolin 
deposits have great length as compared with their width, 
which may be anywhere from 5 to 300 feet. Their depth 
ranges from 20 to 120 feet, depending on the depth to 
which the feldspar has been weathered. 

Quartz and white mica are often present' in kaolin, and it is 
then frequently necessary to put the clay through a washing process 



CLAY 



101 



to remove these minerals. The difference between a washed and 
unwashed kaolin is well shown by the two following analyses, from 
which it is seen that the quartz contents have been considerably 
lowered, and that the washed product approaches more closely to the 
composition of kaolinite : — 





Crude Kaolin 


Washed Kaolin 


Si0 2 


62.40 

26.51 

1.14 

.57 

.01 

.98 

8.80 

.25 

100.66 

66.14 


45.78 


A1 2 0, 


36.46 


Fe 2 3 

FeO 


.28 
1.08 


CaO 


.50 


MgO 

Alkalies 


.04 
.25 


H„0 


13.40 


Moisture 

Clay substance 


2.05 
99.84 
93.24 



North Carolina (44) and Pennsylvania (50, 52) are the 
most important kaolin -producing states, but deposits are 
also worked in Connecticut, Maryland (30), and Virginia 
(59). It is known to occur in Alabama (9). All of these 
deposits except that in Connecticut are found south of 
the limit of the glacial drift. 

The output from the American deposits is insufficient 
to supply the domestic pottery industry, and consequently 
many thousand tons are annually imported from England. 
Since this can be brought over as ballast, it is possible to 
put it on the American market at a low price. The best 
grades of kaolin sell for $10 to $12 per ton at Trenton, 
New Jersey, and East Liverpool, Ohio, these being the two 
most important pottery centers of this country. 



102 ECONOMIC GEOLOGY OF THE UNITED STATES 

Fire Clays. — Fire clays are found in the rocks of all 
systems, from the Carboniferous to the Tertiary, inclusive, 
with the exception of the Triassic. In the Lower Creta- 
ceous of New Jersey (42) there are many beds of refrac- 
tory clay, variable in thickness and closely associated with 
beds of less refractory character. They not only support 
a thriving local fire-brick industry, but serve also as a 
source of supply for factories in other states. Similar, 
but less extensive and less refractory, beds occur in strata 
of Cretaceous Age in the coastal plain of Maryland (30), 
Georgia (17), South Carolina (53), and Alabama (9). 

The most extensive, and among the most important, beds 
of fire clay are those found in the Carboniferous strata of 
Pennsylvania (48, 52), Ohio (46, 47), Kentucky (26, 27), Indi- 
ana (20), and Illinois (19). Those of the first two named 
states are on the average the most refractory. Here the 
fire clays are usually found underlying coal seams and often 
at well-marked horizons, especially in the Upper Productive 
Measures. 

The section given in Fig. 2 is fairly representative of 
their mode of occurrence. 

Those of Indiana and Illinois are so placed that one mine 
shaft is often used for extracting coal, fire clay, stoneware 
clay, and shale. 

The beds of refractory clay, found in the Carbon- 
iferous strata near St. Louis (38), are not only used in the 
manufacture of fire brick, but are, in some cases, found 
suitable, after washing, for mixture with imported Ger- 
man clays for the manufacture of glass pots. The Ter- 
tiary strata of Missouri also supply some refractory 
clays. 



Plate IX 




CLAY 103 

Fire clays are found in the Black Hills of South Dakota (51), in 
the Laramie beds of Colorado (13-15), and in California (12) ; but, except- 
ing near Denver, where used for making fire brick and assayer's appa- 
ratus, these deposits are as yet slightly developed. 

Pottery Clays. — Under this heading are included several 
grades of clay, the kaolins, already described, being the 
purest and best suited to the manufacture of high grades 
of pottery. 

A second grade of pottery clay, the ball clay, is of limited 
distribution in the United States. A small quantity is 
found in the Cretaceous (PI. IX) of New Jersey (42), 
and a much larger amount in the Tertiary of western 
Kentucky (26, 27) and Tennessee (55), and southeastern 
Missouri (38) and Florida (59). As in the case of kaolin, the 
domestic supply is not sufficient to meet the demand, and 
large quantities of ball clay are imported from England. ' 

Stoneware clays form a third grade of pottery clays. 
Being usually of at least semi-refractory character, their 
distribution is essentially coextensive with that of fire 
clays; indeed, the two are often dug from the same pit or 
mine. Large quantities are obtained in New Jersey (42), 
western Pennsylvania (48), and eastern Ohio (47). 

Stoneware clays usually in the same area as the fire clays are also 
obtained in Illinois (19), Indiana (20), Kentucky (26), Tennessee (55), 
Georgia (17), Alabama (9), and Texas (56) ; and they occur also in 
Missouri (38), Iowa (22), Colorado (11), and California (12), although 
little is known about these deposits. 

Many of the Pleistocene surface clays in various states 
are sufficiently dense-burning to be used locally by small 
stoneware factories. 



104 ECONOMIC GEOLOGY OF THE UNITED STATES 

Brick and Tile Clays (59). — None of our states lack an 
abundant supply of good brick and tile clays, and in many 
areas there are extensive deposits near the large markets, 
and often near tide water. In such cases the clay beds 
are exploited to an enormous extent. 

In the northeastern states the Pleistocene surface clays 
are found almost everywhere in great abundance, and are 
made use of in many places, especially near the large cities. 

In the Middle Atlantic states Columbian loams and clay 
marls are an important source of brick material. 

In Ohio, Illinois, and Indiana Pleistocene clays, in part 
of glacial, and in part of flood-plain origin, are much used 
for brick and tile. Impure Paleozoic shales are also used 
in places, especially in the manufacture of vitrified paving 
brick, thousands of which are made annually in Ohio. 
Northern Illinois, Michigan, and Wisconsin draw their main 
supply of brick clays from the calcareous lake deposits. 

Although glacial clays and flood-plain deposits are much 
used in the states west of the Mississippi, the loess which 
occurs over a wide area is probably even more important 
as a source of brick, while in the southwestern states loess 
and adobe are important. Residual clays, river silts, glacial 
clays, and other forms of clay are employed in brick making 
along the Pacific coast. 

Miscellaneous Clays of Importance. — Paper clays of good quality are 
much sought for by paper manufacturers. At present the best ones 
are obtained from the Potomac formation of North Carolina. A small 
amount of glasspot clay (48), comes from western Pennsylvania and 
eastern Missouri ; but our chief supply is imported. Terra-cotta clays 
are obtained from the same areas that supply fire clays, New Jersey 
being the principal producer. 



CLAY 



105 



Uses of Clay. — So few people have even an approxi- 
mate idea of the uses to which clays are put that it seems 
desirable to call attention to them briefly. In the following 
table an attempt has been made to do this: 1 — 

Domestic. — Pottery of various grades; Polishing brick, often known as 
bath bricks; Fire kindlers ; Majolica stoves. 

Structural. — Brick; Tiles and Terracotta; Chimney pots ; Chimney flues ; 
Door knobs ; Fireproofing ; Copings ; Fence posts. 

Hygienic. — Closet bowls ; Sinks, etc. ; Sewer pipe ; Ventilating flues ; 
Foundation Blocks; Vitrified bricks. 

Decorative. — Ornamental pottery ; Terracotta; Majolica; Garden furniture. 

Minor Uses. — Food adulterants ; Paint filler ; Paper filling ; Electrical 
insidations ; Pumps ; Filling cloth ; Scouring soap ; Packing horses' 
hoofs; Chemical apparatus; Condensing worms; Ink bottles; Ultra- 
marine manufacture; Emery wheels. 

Refractory Wares. — Crucibles and other assaying apparatus; Refractory 
bricks of various patterns ; Glass pots. 

Engineering Work. — Puddle; Portland cement; Railroad ballast; Water 
conduits; Turbine wheels. 

Production of Clay. — Owing to the fact that clays are 
usually manufactured by the producer, it is necessary to 
give the value of the product, no record being kept of 
value of the raw material. 

Value of Clay Products in United States, 1901-1903 





1901 


1902 


1903 


Ohio 


$21,574,985 


$24,249,748 


$25,208,128 


Pennsylvania 






15,321,742 


17,833,425 


18,847.324 


New Jersey . 






11,681,878 


12,613,263 


13,416.939 


Illinois . . 






9,642,490 


9,881,840 


11,190.797 


New York 






8,291,718 


8,414.113 


9,208,252 


Indiana . . 






4,466,454 


5,283,733 


5.694,625 


Others . . . 






39,232,320 


44,293,409 


47,396,583 


Total . . 


$110,211,587 


$122,169,531 


$130,962,648 



1 Table compiled by R. T. Hill and modified by H. Ries. 



106 ECONOMIC GEOLOGY OF THE UNITED STATES 



Leading States in Production in 1903 



Common brick .... 
Front brick .... 
Vitrified brick . . . 
Ornamental brick . . 

Fire brick 

Drain tile 

Sewer pipe 

Terra cotta 

Fireproofing .... 
Hollow tile and block . 
Tile, not drain 



Pennsylvania 
Pennsylvania 
Ohio . . . 
Ohio . . . 
Pennsylvania 
Ohio . . . 
Ohio . . . 
Illinois . . 
New Jersey . 
Ohio . . . 
Ohio . . . 



Per Cent of Total 



12.2 
19.7 
28.8 
4.7 
46.4 
24.7 
38.6 
25.6 
46.3 
44.9 
30.5 



REFERENCES ON CLAY 

Technology and Properties. 1. Bain, Min. Indus., VI: 157, 1898. 
(Clay ballast.) 2. Barber, The Pottery and Porcelain of the United 
States, 2d ed., N". Y., 1901 (G. P. Putnam's Sons), $5.00. 
3. Bourry, Treatise on Ceramic Arts, N. Y. (Van Nostrand & Co.), 
London (Scott Greenwood & Co.), 1901. 4. Bischof, Die Feuer- 
festen Thone, 2d ed., Leipzig, 1895 (Quandt & Handel), 12 Mks. 
5. Branner, Bibliography of Clays and the Ceramic Arts, U. S. Geol. 
Surv., Bull. 143, Washington, 1896. 7. Davis, A Practical Treatise 
on the Manufacture of Bricks, Tiles, and Terra Cotta, 2d ed., Philadel- 
phia, $5.00. 8. Wheeler, Vitrified Paving Brick, Indianapolis, 1895, 
(Clay worker Pub. Co.), $1.00. Many excellent papers in Transac- 
tions American Ceramic Society, Vols. 1-6 of which have appeared. 
See also Nos. 22, 30, 42, 43 for general properties and technology. 

Areal Reports. — Alabama : 9. Smith and Ries, Ala. Geol. Surv., 
Bull. 6, 1900. (General.) — Arkansas : 10. Branner, Ark. Geol. 
Surv., Rept. for 1888. (Many analyses.) 11. Also Amer. Inst. Min. 
Engrs., Trans. XXVII: 42, 1898. (S. W. Ark.) — California : 
12. Johnston, Calif. State Mineralogist, 9th Ann. Rept.: 287, 1890. 
(General.) See also scattered notices in other annual reports. — 
Colorado: 13. Eldridge, U. S. Geol. Surv., Mon. XXVII, 1896. 
(Denver Basin.) 14. Geijsbeek, Clay Worker, XXXVI : 424, 1901. 
(General.) 15. Ries, Amer. Inst. Min. Eugrs., XXII: 386, 1897. 
(Clays and Clay Industry.) — Delaware : 16. Booth, Geol. of Dela- 



CLAY 107 

ware: 94 and 106, 1841. — Georgia : 17. Ladd, Ga. Geol. Surv., Bull. 
6 A., 1898. (Cretaceous clays.) 18. Spencer, Ga. Geol. Surv., Paleo- 
zoic Group : 276, 1893. (N. W. Ga.) — Illinois : 19. Many scattered 
references in volumes on Economic Geology of Illinois Geol. Survey, 
Resume of these in U. S. Geol. Surv., Prof. Pap. 11, 1903. — Indiana: 
20. Blatchley, Ind. Dept. Geol. and Nat. Hist., 20th Ann. Rept. : 23, 
1896. (Carboniferous clays.) 21. Same author, 22d Ann. Rept. : 
105, 1898. (N. W. Ind.) Scattered references in other annual re- 
ports. — Iowa : 22. Beyer, Williams, and Weems, la. Geol. Survey, 
XIV: 29, 1904. — Kansas : 23. Prosser, U. S. Geol. Surv., Mineral 
Resources, 1892: 731, 1893. 24. See also Reports on Mineral 
Resources of Kansas, Kas. Geol. Survey, 1897-1901. — Kentucky : 
25. Crump, Eng. and Min. Jour., LXIV : 89, 1897. 26. Ries, U. S. 
Geol. Surv., Prof. Pap. 11, 1903. 27. Many analyses in Ky. Geol. 
Surv., Chem. Rept. A, pts. 1, 2, and 3, 1885, 1886, 1888.— Louisiana : 
28. Clendenin, Eng. and Min. Jour., LXVI : 456, 1898. 29. Ries, 
Preliminary Report on Geology of La., I: 264, 1899. — Maryland: 

30. Ries, Md. Geol. Surv., IV, Pt. Ill: 205, 1902. — Massachusetts: 

31. Crosby, Technol. Quart., Ill : 228, 1890. (Kaolin at Blandford.) 

32. Shaler, Woodworth, and Marbut, U. S. Geol. Surv., 17th Ann. 
Rept., 1 : 957, 1896. (R. I. and S. E. Mass.) 33. Whittle, Eng. and Min. 
Jour., LXVI: 245, 1898. —Michigan: 34. Ries, Mich. Geol. Surv., 
VIII : Pt. I, 1903. (Clays and shales.) — Minnesota : 35. Berkey, 
Amer. Geol., XXIX: 171, 1902. (Origin and distribution.) 36. Win- 
chell, Minn. Geol. Surv., Misc. publications, No. 8, 1881. (Brick 
clays.) — Mississippi : 37. Eckel, U. S. Geol. Surv., Bull. 213 : 382, 
1903. (N. W. Miss.) —Missouri: 38. Wheeler, Mo. Geol. Surv., XI, 
1896. (General.) — Nebraska : 39. Neb. Geol. Surv., I: 202, 1903.— 
New Hampshire : 40. Hitchcock and Upham, Report on Geology of 
New Hampshire, V: 85, 1878. — New Jersey: 41. Cook, N. J. Geol. 
Surv., 1878. (Special Report on Clays.) 42. Kummel, Ries, Knapp, 
N. J. Geol. Surv., Final Reports, VI, 1904. — New York: 43. Ries, 
N. Y. State Museum, Bull. 35, 1900. (General.) — North Carolina: 
44. Ries, N. Ca. Geol. Surv.,. Bull. 13, 1897. (General.) —North 
Dakota : 45. Babcock, N. D. Geol. Surv., 1st Rept. : 27. (General.) 
— Ohio: 46. Orton, Ohio Geol. Surv., VII > 45, 1893. (Geology.) 

47. Orton, Jr., Ibid., p. 69. (Clay industries.) — Pennsylvania : 

48. Hopkins, Pa. State College, Ann. Repts. as follows, 1897, Ap- 
pendix. (W. Pa.) 49. Ibid., Append, to Rept. for 1899-1900. 
(Philadelphia and vicinity). 50. Ibid., 1898-1899. (S. E. Pa.) 
51. Many analyses in 2d Pa. Geol. Surv., Rept. MM. : 257, 1879, 
and scattered references in Repts. H 5, H 4, C 4, C 5, etc. 52. Re- 
sume in U. S. Geol. Surv., Prof. Pap. 11 : 208, 1903. — South Carolina : 



108 ECONOMIC GEOLOGY OF THE UNITED STATES 

53. Sloane, Bull. S. Car. Geol. Surv. (S. Car.) — South Dakota: 54. 
Todd, S. D. Geol. Surv. ; Bull. 1: 108. — Tennessee : 55. Eckel, 
U. S. Geol. Surv., Bull. 213 : 382, 1903. (W. Tenn.) — Texas : 56. See 
county reports issued by First Geol. Survey. — United States : 57. Hill, 
U. S. Geol. Surv., Min. Res. 1891 : 474, 1893. 58. Ries, U. S. Geol. 
Surv., 18th Ann. Kept., IV : 1105, 1897. (Pottery Clays.) 59. Ries, 
U. S. Geol. Surv., Prof. Pap. 11, 1903. (Clays east of Mississippi 
River.) — Vermont : 60. Nevius, Eng. and Min. Jour., LXIV: 189, 
1897. (Kaolin.) 61. Ries, U. S. Geol. Surv., Prof. Pap. 11 : 58, 
1903. — Washington: 62. Landes, Wash. Geol. Surv., II: 173, 1902. 
(General.) — Wisconsin: 63. Buckley, Wis. Geol. and Nat. Hist. 
Surv., Bull. 7, Pt. I, Eco. Series 4, 1901. (General.) 64. Forth- 
coming bulletin by Ries. — Wyoming : 65. Knight, Wyo. Experiment 
Station, Bull. 14, 1893. (General.) 



CHAPTER V 

LIME AND CALCAREOUS CEMENTS 

Composition of Limestones (35) . — Limes and calcareous 
cements form an important class of economic products, 
obtained from limestones by heating them to a tempera- 
ture ranging from that of decarbonation to clinkering. 
The term limestone is applied to one of the main divi- 
sions of the stratified rocks so widely distributed, both 
geologically and geographically, and formed under such 
different conditions, that its composition varies greatly, 
this range of variation becoming appreciable from an 
inspection of the following table, which contains a few 
selected types : * — 

Table of Limestone Analyses, including the Minerals 
Calcite and Dolomite 





CaC0 3 


MgC0 3 


Si0. 2 


A1,0 3 


Fe 2 3 


H. 2 


1. Calcite .... 

2. Dolomite . . . 

3. White limestone, 

Adams, Mass. . 

4. Limestone, Lehigh 

Valley district, 
Pa 

5. Limestone, Coplay, 

Pa 


100.00 
54.35 

99.30 

88.00 
67.14 


45.65 
.49 

4.00 
2.90 


.63 

5.87 
18.34 


.55 

1. 

7 


59 
49 


3.92 



Kemp, " Handbook of Rocks.' 
109 



110 



ECONOMIC GEOLOGY OF THE UNITED STATES 



6. Limestone, Cum- 

berland, Md. 

7. Dolomite, Pleasant- 

ville, N.Y. . . 

8. Magnesian lime- 

stone, Rosendale, 
N.Y 



CaC0 3 



41.80 
59.84 

45.91 



MgCO a 



8.60 
36.80 

26.14 



SiOo 



24.74 
2.31 

15.37 



AloO s 



16.74 
.40 



Fe 2 3 



6.30 
.25 



11.38 

( 



H,0 



1.20 



From this table it will be seen that limestones vary from 
rocks composed almost entirely of carbonate of lime, or of 
carbonate of lime and carbonate of magnesia, to others 
which are high in clayey or siliceous impurities. The 
presence of such impurities in large quantity usually 
imparts an earthy appearance to the limestone, and some- 
times even gives it a shaly structure. 

Marked variations in composition may at times be found 
even in a single quarry, while in other cases a limestone 
formation may show remarkable uniformity of composition 
over a wide area. 

Changes in Burning (8, 35).— When limestones are cal- 
cined or u burned" to a temperature sufficiently high to 
drive off volatile constituents, such as carbon dioxide, 
water, and sulphur (in part), or, in other words, to the 
point of decarbonation, the rock is left in a more or less 
porous condition. If heated to a still higher temperature, 
the rock clinkers or fuses incipiently, but the temperature 
of clinkering depends on the amount of siliceous and clayey 
impurities in the rock. 

Lime (5, 8) . — Limestone free from or containing but a 
small percentage of argillaceous impurities is, by decarbona- 



LIME AND CALCAKEOUS CEMENTS 111 

tion, changed to quicklime, a substance which has a high 
affinity for water, and which, when mixed with water, 
"slakes," forming a hydrate of lime. This change is 
accompanied by the evolution of heat and by swelling, 
and this action becomes the more marked the higher the 
percentage of lime carbonate in the rock, for the slaking 
activity is retarded by the presence of magnesium carbon- 
ate, and especially by argillaceous impurities. Limes have, 
therefore, been divided into " fat " limes and " meager " 
limes, depending on the rapidity with which they slake 
and the amount of heat they develop in doing so (5). 

Hydraulic Cements. — With an increase in clayey and 
siliceous impurities, the burned rock shows a decrease in 
slaking qualities, and develops hydraulic properties, or sets 
when mixed with water, and even under the same. Products 
of this type are termed cements, and owe their hydraulic 
properties to the formation during burning of silicates and 
aluminates of lime. On mixing the burned ground rock 
with water, these take up the latter and crystallize, thereby 
producing the set of the cement. 

Hydraulic cements can be divided into the following 
classes: Pozzuolano cements, hydraulic limes, natural ce- 
ments, and Portland cements. 

Pozzuolano Cements (2,9,41). — These are produced from 
an uncalcined mixture of slaked lime and a silico-aluminous 
material, such as volcanic ash or blast-furnace slag. 

This process was known to the ancients, and is named 
from its early use around Pozzuolano, Italy. The composi- 
tion of an Italian Pozzuolano earth may vary between the 
following limits (9): Si0 2 , 52-60; A1 2 3 , 9-21; Fe 2 3 , 



112 



ECONOMIC GEOLOGY OF THE UNITED STATES 



5-22; CaO, 2-10; MgO, up to 2; alkalies, 3-16; H 2 0, 
up to 12. 

The manufacture of slag cement is now carried on at 
several localities in the United States, and is a growing 
industry (2). 

Hydraulic Limes (9) are formed by burning a siliceous 
limestone to a temperature not much above that of decar- 
bonation. Owing to the high percentage of lime carbon- 
ate, considerable free lime appears in the finished product. 
Hydraulic limes generally have a yellow color, and a gravity 
of about 2.9. They slake and set slowly, and have little 
strength unless mixed with sand. This class is of little im- 
portance in the United States, but much more so in Europe. 

Natural Cements (1, 8, 9, 41). — These, known also as Roman 
cement, quick-setting cement, and Rosendale cement, are 
made by burning a silico-aluminous limestone (containing 
from 15 to 40 per cent clayey impurities) at a temperature 
between decarbonation and clinkering. The product shows 
little or no free lime. The following analyses will give 
some idea of the range in composition of natural cement 
rocks quarried in the United States : — 

Analyses of Certain American Cement Rocks 





CaC0 3 


MgC0 8 


Si0 2 + 
Insol. 


Fe 2 3 


A1 2 3 


Alka- 
lies 


H 2 


Un- 

DET. 


Rosendale, N".Y. 


45.91 


26.14 


15.37 


11. 


38 




1. 


20 


Utica, 111. . . . 


42.25 


31.98 


21.12 


1. 


12 




1.07 


2.46 


Milwaukee, Wis. 


45.54 


32.46 


17.56 


3.03 


1.41 








Fort Scott, Kas. 


65.21 


10.65 


15.21 




4.56 






4.37 


Cement, Ga. . . 


43.50 


22.00 


22.10 


1.80 


5.45 


.22 


4.95 




Coplay, Pa. . . 


67.14 


2.90 


18.34 


7. 


49 


.19 




3.94 



LIME AND CALCAREOUS CEMENTS 



113 



Natural cements differ from lime in possessing hydraulic 
properties, and refusal to slake unless ground very fine. 
They differ from Portland cements in lighter weight, lower 
temperature of burning, quicker set, lower ultimate strength, 
and greater latitude of composition. Magnesia is not re- 
garded as a detrimental impurity in natural cements as it 
is in Portland cement. 

The following are some analyses of the burned material : — 

Analyses of Some Natural Rock Cements 





CaO 


MgO 


Si0 2 


A1 2 3 


Fe 2 3 


Na 2 0,K 2 Ignition 


Natural rock cement, 
















Rosendale, N.Y. 


34.38 


18 


30.5 


6.84 


2.42 


3.98 


3.78 


Natural rock cement, 
















Akron, N.Y. . . 


40.68 


22 


22.62 


7.44 


1.40 


2.23 


3.63 


Natural rock cement, 
















Cumberland, Md. . 


43.97 


2.21 


22.38 


11.71 


2.29 


9. 


2.44 


Roman cement, Rii- 
















dersdorf, Germany . 


56.45 


4.84 


27.88 


6.19 


4.64 







Portland Cement (4, 6, 7, 10, 41). — This term is applied to 
artificial mixtures of clay and lime rock, which are burned 
to a temperature of clinkering. Portland cement was first 
made by Joseph Apsdin, of Leeds, England, who desired 
to make an artificial cement that would replace natural 
hydraulic cements. It received its name because it hard- 
ened under water to a mass resembling the Portland stone 
of England. 

The three essentials for Portland cement are lime, silica, 
and alumina, and it is consequently necessary to use raw 
materials supplying these three substances in the proper 
quantities. This is in all cases done by artificial mixture, 



114 ECONOMIC GEOLOGY OF THE UNITED STATES 

and many of the so-called "natural" Portland cements 
used in the United States are not strictly such. The fol- 
lowing six combinations of materials are at present used 
in the manufacture of true Portland cement in the United 
States: marl and clay ; limestone and clay, or shale; 1 chalk 
and clay ; pure limestone and argillaceous limestone; alkali 
waste and clay ; limestone and slag. 

In the first four of these combinations it is evident that the sub- 
stances first named supply the lime and the second the silica and 
alumina. In the fourth the argillaceous limestone supplies some lime, 
as well as the silica and alumina. The nature of the raw materials 
chosen depends to a large degree on the location of the plant, whether 
in a limestone or a marl producing region. Where both of these raw 
materials are available, as in parts of New York, questions of manipu- 
lation in the process of manufacture govern the selection of one or 
the other. 

Marls, for example, though easier to excavate and reduce than lime- 
stones, contain so much more organic matter and water than limestones 
that they are more expensive to handle and prepare. Marl beds are 
likewise apt to be of limited extent and irregular, while limestone 
beds are, so far as the needs of a manufacturing plant are concerned, 
practically limitless. 

Comparing clay and shale, the former is often easier to excavate, 
but, on account of the water it contains, has to be dried before it can 
be ground and mixed. The fossils in shales are sometimes an impor- 
tant source of calcium carbonate, and then careful grinding and mixing 
is necessary to bring about a uniform distribution of the lime through 
the mass. Shale is, however, used by only a few works. 

Argillaceous limestone, mixed with a much smaller quantity of purer 
limestone, as in Pennsylvania and New Jersey, is superior to a lime- 
stone and clay mixture, because less thorough mixing and fine grinding 
are required. In such cements, even when grinding and mixing are 

1 It is probable that the refuse of many slate quarries could also be used 
in place of shale. 



LIME AND CALCAREOUS CEMENTS 



115 



incompletely done, the particles of argillaceous limestone so closely 
resemble the proper mixture in chemical composition as to affect the 
result but little. 

The following table gives the analyses of some of the 
raw materials used in manufacture of Portland cement: — 

Analyses of Raw Materials used for Portland Cement 

















H 2 + 




Locality 


Material 


Si0 2 


A1 2 3 


Fe 2 3 


CaC0 3 


MgC0 3 


Org. 
Matter 


MlSCEL. 




' Calc. shale 
















Lehigh 


or 














CaS0 4 


Valley, 


cement rock 
Limestone 


15.40 

5.87 


4.26 


1.38 


74.66 

88.00 


2.66 
4.00 


1.88 


.86 


Penn. 


1.59 






Mixture 

r 


13.97 


5.07| 1.88 


74.1 
CaO 


2.04 
MgO 


1.82 




Glens 
Falls, 
N.Y. 




S0 3 


Limestone 


3.3 


1.3 


52.15 


1.58 




.3 








CaO 


MgO 




SO g 


I Clay 


55.27 


28.15 


5.84 


2.25 


8.37 


.12 


Warners, 


[Marl 
I Clay 


.26 


.10 


94.39 


.38 


4.64 




N.Y. 


40.48 


20.95 


25.80 


.99 


8.50 






, 


Insol. 










CaS0 4 


Sandusky, 


Marl 


1.28 


1.72 


92.70 


.50 


1.13 


2.06 


Ohio 


J 








CaO 


MgO 








I Clay 


64.70 


11.9 


9.9 


.90 


.70 


11.9 




White 


f Chalk 


41.20 


2.21 


1.03 


95.29 








Cliffs, 










CaO 


MgO 






Ark. 


I Clay 


53.3 


23.29 


9.52 


.36 


1.49 


5.16 





In the selection of raw materials the aim of the manu- 
facturers is to produce a raw mixture which runs approx- 
imately 70 to 75 per cent lime carbonate and the balance 
clay (U. S. Geol. Surv., 21st Ann. Rept., VI : 404, 1900). 
The proportions of clay and lime rock used at each factory 
are not always disclosed, and the mixture of the two in- 



116 



ECONOMIC GEOLOGY OF THE UNITED STATES 



gredients is kept under careful control by frequent chemical 
analysis, since slight variations from the proper composi- 
tion may injure the cement. The following analyses will 
serve to illustrate the composition of some American Port- 
land cements : — 



Analyses of Cements 





Si0 2 


A1 2 3 


Fe 2 3 


CaO 


MgO 


so 3 


Empire brand . . 
Sandusky . . . . 
Alpha 


22.04 
23.08 
22.62 


6.45 
6.16 
8.76 


3.41 
2.90 
2.66 


60.92 
62.38 
61.46 


3.53 
1.21 
2.92 


2.73 
1.66 
1.53 





Distribution of Lime and Cement Materials in the United 
States. Limestone for Lime. — Limestones of suitable com- 
position for burning lime are so widely distributed that no 
particular regions or states require special mention. 1 In the 
New England states, crystalline limestones are the chief 
source of supply. In the Appalachian states, from New 
York to Alabama, there are many Paleozoic limestones of 
high purity, notably the Trenton, Lower Helderberg, and 
Carboniferous limestones (see state references). The same 
series of rocks are also of importance in the Mississippi 
Valley states from Tennessee to Michigan (27). Lime of 
excellent quality is obtained from the Subcarboniferous in 
Iowa (41), Kansas (21), and Missouri (41), and from the 
Cretaceous in Texas (41). Limestones suitable for lime 
manufacture are also found in numerous localities in the 
Pacific coast states (41). 



1 Analyses and detailed descriptions will be found in the areal reports, 
mentioned in the list of References. 



Plate X 




Fig. 1. —Quarry of natural cement rock, Cumberland, Md. Photo, by H. Ries. 




Fig. 2. — Marl pit at Warners, 1N.Y. The dark streaks are peat, and the marl is 
underlain by clay. Photo, by H. Ries. 



LIME AND CALCAREOUS CEMENTS 117 

Hydraulic Limes. — Largely because of the great abun- 
dance of natural rock cements, which are of superior value, 
these materials, though much used abroad, are of no im- 
portance in the United States. 

Natural Rock Cements (1, 41). — Calcareous rocks of this 
class are found at a number of points, mainly in the Paleozoic 
formations. In 1903 they were worked in sixteen different 
states, eleven of which are east of the Mississippi. These 
are found at a number of points in the Appalachian region, 
but, owing to the folded character of the beds (PL X, Fig. 
1), their extraction is often difficult. The most important 
natural rock cement region of the United States is that of 
Rosendale, New York (32, 35), where the cement rocks are 
found in the Water Lime beds at the base of the Lower 
Helderberg, being obtained from underground workings. 
There are two beds, separated by a few feet of limestone, 
and often dipping at a high angle. Their thickness ranges 
from 7 to 25 feet. The great development of this region is 
due partly to the large supply of raw material, and partly 
to the proximity to New York City and the possibility of 
shipment by tide-water. 

Farther west, around Akron, New York, and Buffalo (31), 
the cement rock occurs at a somewhat higher horizon. In 
eastern Pennsylvania, especially in the vicinity of Coplay 
and Catasauqua (39), cement rock of Trenton age occurs in 
a region of marked folding. This region, though an im- 
portant producer of cement rock, is even more important as 
a producer of Portland cement (41). 

The Water Lime beds again form an important source of 
cement rock in the vicinity of Cumberland, Maryland (24) 
(PL X, Fig. 1), where there are four beds of economic 



118 ECONOMIC GEOLOGY OF THE UNITED STATES 

value, ranging from 6 to 17 feet in thickness, and separated 
by calcareous shales. The entire series is highly folded, the 
dip sometimes being as much as 90°. 

Cement rock is also obtained in southeastern Ohio (36); 
at Louisville, Kentucky (23), probably the second most im- 
portant center in the United States ; in the Hamilton rocks 
at Milwaukee, Wisconsin (44); and at Utica and La Salle, 
Illinois (17), where it is found in the Calciferous formation 
in a bed from 6 to 8 feet thick. 

Portland Cements. — Clay and limestone, in one form or 
another, are so widely distributed throughout the United 
States, that it is possible to manufacture Portland cement 
at many localities, and the geologic age of the materials 
used ranges from Ordovician to Pleistocene (41). Nine- 
teen states were making this cement in 1903, the factories 
being spread over the country from the Atlantic to the 
Pacific (41). 

By far the most important district is the Lehigh Valley 
in Pennsylvania, which supplies about 70 per cent of the 
domestic product. Here the raw materials consist of beds 
of argillaceous limestone and nearly pure limestone, this 
being one of the few localities where such a mixture is 
obtainable. The same beds are found in the adjacent terri- 
tory of New Jersey (30). 

In the eastern half of New York (35) the Ordovician and 
Silurian limestones form an inexhaustible supply of material 
to mix with Pleistocene surface clays. In the south central 
part of New York the Tully limestone and Hamilton shales 
are employed, while in the central and southwestern portion, 
beds of marl (PI. X, Fig. 2), associated with surface clays, 
are utilized. 



LIME AND CALCAREOUS CEMENTS 119 

Ohio (36, 41), Indiana (18), and Michigan (26, 28) are 
important Portland cement producing states. The abun- 
dance of marl and Pleistocene clays makes them the favorite 
materials, notwithstanding the fact that beds of Paleozoic 
limestones occur in each of the states. Marl, although espe- 
cially abundant in Michigan, is found in many states lying 
east of the Mississippi and north of the terminal moraine. 
It is precipitated from the waters of ponds through the 
agency of minute plants, especially Chara (26). 

In Kansas Carboniferous shales and limestones are used 
for making Portland cement (21, 22), and in Texas and 
Arkansas the Cretaceous shales and chalky limestones are 
employed (13, 14) ; Alabama has a Tertiary limestone of 
such composition that very little pure limestone has to be 
added to it (12). Portland cement is also manufactured in 
North Dakota (41), South Dakota (41), Utah (41), Colorado 
(41), and California (15). 

Uses of Lime. — The most important single use of lime 
is for mixing with sand to form mortar, and many thousands 
of tons are used annually for this purpose. In addition 
to this use, lime is employed for a great variety of pur- 
poses, of which the following are the most important : as 
a purifier in basic steel manufacture; in the manufacture 
of refractory bricks, ammonium sulphate, soap, bone ash, 
gas, potassium-dichromate, paper, pottery glazes, and cal- 
cium carbide ; as a disinfectant ; as a fertilizer ; as a polish- 
ing material ; for dehydrating alcohol, preserving eggs, and 
in tanning. 

Uses of Cement. — The use of hydraulic cement is con- 
stantly increasing in the United States, this being specially 



120 



ECONOMIC GEOLOGY OF THE UNITED STATES 



true of Portland cement, which is superseding natural 
cement to a great extent, and is finding an increasing use 
in building and engineering operations. For pavements, 
Portland cement is probably more extensively used in 
America than in any other country; and as an ingredient 
of concrete it is widely employed. Blocks weighing as much 
as 65 to 70 tons have been made for harbor improvements 
at New York City (37 a). 



Production of Cement. — The following tables give the 
production of natural-rock and Portland cement. Those 
given for the latter cover a greater period than those of the 
former, and are grouped with figures of import and consump- 
tion in order to show more clearly the tremendous growth 
of the American Portland cement industry. 

Production of Natural Cement in United States 





1901 


1902 


1903 




Quantity 


Value 


Quantity 


Value 


Quantity 


Value 




barrels 




barrels 




barrels 




New York . 


2,234,131 


$1,117,066 


3,577,340 


$2,135,036 


2,417,137 


$1,510,529 


Pennsylvania . 


942,364 


376,954 


796,876 


340,669 


1,339,090 


576,269 


Indiana ] 
Kentucky j 


2,150,000 


752,500 


1,727,146 


869,163 


533,573 


766,786 


Wisconsin . . 


481,020 


182,788 


437,913 


162,628 


330,522 


139,373 


Illinois . . . 


469,842 


187,936 


607,820 


156,855 


543,132 


178,900 


Maryland . . 


351,329 


175,665 


409,200 


150,680 


269,957 


138,619 


Others . . . 


456,137 


263,369 


488,010 


261,599 


569,860 


365,044 


Total . . 


7,084,823 


$3,056,278 


8,044,305 


$4,076,630 


7,030,271 


$3,675,520 



LIME AND CALCAREOUS CEMENTS 121 

Production of Portland Cement in United States 





1891 


1900 


1901 1902 


1903 


Production of United States 
Imports 


barrels 

4.54,813 

2,988,313 


barrels 
8,482,020 
2,386,683 


barrels 
12,711,225 
922,426 


barrels 

17,230,644 

1,961,013 


barrels 

22,342,973 

2,251,969 


Total 


3,443,126 


10,868,703 


13,633,651 


19,191,657 


24,594,942 


Exports (domestic and for- 
eign) 


— 


139,939 


417,625 


373,414 


285,463 


Total consumption . . 
Percentage of domestic 
production to total con- 
sumption in United States 


3,443,126 
13.2 


10,728,764 
79.1 


13,216,026 
96.2 


18,818,248 
91.6 


24,309,479 
91.9 



Production of Portland Cement by States in 1903 





Barrels 


Value 


Pennsylvania 

New Jersey 

Michigan 

Illinois 


9,754,313 
2,693,381 
1,955,183 
1,257,500 
1,077,137 
1,019,682 
720,519 
3,856,258 


$11,205,892 
2,944,604 
2,674,780 
1,914,500 
1,347,797 
1,285,310 
998,300 
5,342,136 


Indiana 

Kansas 


Ohio 

All others 




Total 


22,342,973 


$27,713,319 





REFERENCES ON LIME AND CEMENT MATERIALS 

Technology. 1. Cummings, American Cements, Boston, 189S. (Many 
analyses.) 2. Eckel, Min. Indus. X : 84, 1902. (Slag cement manu- 
facture.) 3. Eckel, Amer. Geol. XXIX: 146, 1902. (Classifica- 
tion.) 4. Green, Portland Cement Industry of the World, Journal 
of Association of Civil Engineering, XX: 391, 1898. 5. Gilmore, 
Practical Treatise on Limes, Hydraulic Cements and Mortars, X. Y., 
D. Van Xostrand, 1872. 6. Jameson, Portland Cement; its Manu- 
facture and Use, Xew York, 1898. 7. Lewis, Manufacture of 



122 ECONOMIC GEOLOGY OF THE UNITED STATES 

Hydraulic Cement in United States, Mineral Industry, VI: 91, 1898. 
8. Richardson, Series of Articles on Lime and Cement Mortars 
in the Brickbuilder, 1897 and 1898. 9. Schoch, Die Moderne 
Aufbereitung u. Wertung der Mortel-Materialien, Berlin, 1896. 
10. Spalding, Hydraulic Cement ; its Properties, Testing, and Use, 
New York, 1897, John Wiley & Sons. 
Locality Reports. Alabama: 11. Meissner, Ala. Ind. and Sci., 
Proc, IV: 12. (Birmingham district limestone.) 12. Smith, Ala. 
Geol. Surv., Bull. 8, 1904. (Many analyses.) — Arkansas: 13. Bran- 
ner, Amer. Inst. Min. Engrs., Trans. XXVII : 42, 1898. (S. W. 
Ark.) 14. Taff, U. S. Geol. Surv., 22d Ann. Kept., 111:687, 1902. 
(S. W. Ark.) — California: 15. Grimsley, Eng. and Min. Jour., 
LXXII: 71, 1901. (Cement industry.) 16. Irelan, 8th Ann. Rept. 
State Mineralogist : 865 and 888, 1888 ; also 9th Ann. Rept. : 
309-311, 1889; 13th Ann. Rept. Calif. State Mineralogist: 627, 
1896 ; 12th Ann. Rept. : 391, 1894. (Cements.) —Illinois : 17. Free- 
man, Amer. Inst. Min. Eng., Trans. XIII: 172, 1885. (La Salle, 
natural rock cement.) — Indiana: 18. Blatchley, 25th Ann. Rept. 
Ind. Dept. Geol. and Nat. Res., 1900: 323, 1901. (Bedford lime- 
stone.) 19. Siebenthal, 25th Ann. Rept. Ind. Dept. Geol. and 
Nat. Hist. 1900 : 331, 1901. (Silver Creek hydraulic limestone.) — 
Iowa : 20. Houser, la. Geol. Surv., 1 : 199, 1893. (Niagara lime- 
stone.) — Kansas : 21. Haworth, Kas. Geol. Surv., Ill: 31, 1898. 
22. Haworth and Schrader, U. S. Geol. Surv., Bull. 260 : 506, 1905. 
(Independence Quadrangle.) — Kentucky : 23. Kentucky Geol. Surv., 
New Series, IV : 404. — Maryland : 24. Clark and others, Md. Geol. 
Surv. Rept. on Allegheny Co. : 185, 1900. (Lime and cements.) 
25. Martin, Md. Geol. Surv. Rept. on Garrett Co.: 220, 1900.— 
Michigan : 26. Hale and others, Mich. Geol. Surv., VIII, Pt. 3, 1903. 
(Marl fox Portland cement.) 27. Lane, Eng. and Min. Jour., LXXI : 
662, 693, and 725, 1901. (Mich, limestones.) 28. Russell, U. S. Geol. 
Surv., 22d Ann. Rept., Ill: 629, 1902. (Mich. Portland cement 
industry.) — Mississippi : 29. Crider, U. S. Geol. Surv., Bull. 260: 
510,1905. (N. E. Miss.) — New Jersey: 30. Kiimmel, Ann. Rept. 
N. J. State Geologist, 1900 : 9. (N. J. Portland cement industry.) — 
New York : 31. Bishop, 15th Ann. Rept. N. Y. State Geologist : 338, 
1897. (Erie Co.) 32. Nason, Rept. of N. Y. State Geologist, 1893 : 
375. (Ulster Co.) 33. Pohlman, Amer. Inst. Min. Eng., Trans. 
XVIII : 250, 1889. (Cement rock at Buffalo.) 34. Ries, U. S. Geol. 
Surv., 17th Ann. Rept., Ill (cont.) : 795, 1896. (Limestone quarries, 
New England and New York.) 35. Ries and Eckel, Bull. N. Y. 
State Museum, 41, 1901. (N. Y. lime and cement industry.) — Ohio : 
36. Lord, Ohio Geol. Surv., VI : 671, 1888. (Natural and artificial 



LIME AND CALCAREOUS CEMENTS 123 

cements.) 37. Orton, Ohio Geol. Surv., VI : 703, 1888. (Lime.) 
37 a. Eno, Ohio Geol. Surv., 4th Series, Bull. 2, 1904. (Uses of 
cement.) 376. Bleininger, Ibid., Bull. 3. (Manufacture of cement.) 
— Pennsylvania: 38. Prime, Second Geol. Surv. of Pa., Rep. DD : 59, 
1878. 39. Eckel, U. S. Geol. Surv., Bull. 225 : 448, 1904. (Lehigh 
district.) 40. Stone, U. S. Geol. Surv., Bull. 260, 1905. (Limestones, 
S. W. Pa.) —United States : 41. Eckel, U. S. Geol. Surv., Bull. 260 : 
497, 1905. Also Bull. 243. (Cement resources and industry.) — Vir- 
ginia: 42. Catlett, U. S. Geol. Surv., Bull. 225 : 457, 1904. (Cement 
resources, Valley of Va.) 43. Also Bassler, Ibid., Bull. 260: 531, 
1905.— Wisconsin: 44. Chamberlin, Geol. of Wis., II, Pt. 2: 395, 
1873. (Xatural rock cement.) 



CHAPTER VI 



SALINES 



Salt. — Common salt, the chloride of sodium (NaCI), is 
a widely distributed mineral, being found, (1) in solution 
in sea water or salt lakes ; (2) as solid masses termed rock 
salt ; (3) as natural brine in cavities or pores of the rocks, 
from which it may exude as salt springs or be tapped by 
wells ; and (4) in marshes and soils. 

Although all four of these methods of occurrence may 
serve as commercial sources of salt, it is only the second 
that is of great economic importance. 

Occurrences of Salt in Sea and Lake Waters. — Salt is 
present in all ocean water, and also in that of most inland 
lakes or seas having no outlet. As can be seen from the 
following analyses, the percentage of salt is greater in some 
salt lakes than in the ocean : — 





CO H 

H & 

< © 
02 02 


M 

w 

H 


Percentage of 


3alts in Solid 


Matter 


Locality 




3 


5 

bo 


u u 
P3 « 

cs to 
6£ 


o 

Q 


O 

02 

be 


o o 
oo 
a be 

OS 


Black Sea .... 
Mediterranean Sea . 
Atlantic Ocean . . 


1.77 
3.37 
3.63 

22.30 

14.99 


98.23 
96.63 
96.37 

77.70 

85.01 


79.39 
77.03 
77.07 

36.55 

79.12 


1.07 
2.48 
3.89 

4.57 

.57 


7.38 
8.76 
7.86 

45.20 

9.93 


.03 

.49 

1.30 

.85 


.60 
2.76 
4.63 

.45 

.56 


8.32 
8.34 
5.29 

6.21 


3.21 
.10 


Dead Sea .... 


CaC'] 2 
11.38 


Great Salt Lake . . 


K 2 S0 4 
3.47 



124 



SALINES 125 

Salt is sometimes obtained by artificial evaporation from 
both the ocean and salt lakes ; but in the United States this 
plan is profitable only under exceptional conditions, as around 
San Francisco Bay, California (6), or Great Salt Lake, Utah. 

Rock Salt. — Rock salt, which is the most important source 
of commercial salt, is present in layers of variable thickness 
and purity embedded with sedimentary rocks, such as shales 
or sandstones. It is frequently associated with gypsum, and 
less commonly with limestone, or easily soluble compounds 
of magnesia, potash, and lime. The salt beds vary in thick- 
ness from a few inches up to as much as 3600 feet (Speren- 
berg, Germany), and while found in all geological formations 
from the Cambrian to the Pleistocene, except the Creta- 
ceous, the rock salt of the United States is not found in 
formations older than the Upper Silurian. 

Origin of Bock Salt (5). — One of the interesting problems 
of geology has been to find a correct theory to account for 
salt deposits of enormous thickness and often high purity. 
It is well known that salt is deposited in the course of 
evaporation of inland seas, such as the Dead Sea, and this 
is perhaps the origin of some of the salt beds found in the 
strata. But in many cases the material was evidently de- 
posited in close connection with the open ocean, being both 
overlain and underlain by massive sediments with which 
it is directly continuous. It is inconceivable that such 
beds were precipitated in the open ocean, though they may 
well have been formed in seas or bays more or less com- 
pletely cut off from the ocean. 

This explanation, elaborated by Ochsenius (4), assumes 
a barrier partly shutting out the ocean water. Evaporation 



126 ECONOMIC GEOLOGY OF THE UNITED STATES 

on the inclosed area of the sea exceeds the supply of water 
from inflowing rivers and from the open ocean. Therefore 
the water on the surface of the sea becomes more dense and 
settles to the bottom of the basin, being prevented from 
escape into the open ocean by the barriers at the entrance. 
As the surface of the bay is lowered by evaporation, ocean 
water enters, furnishing a constant supply of salt. If the 
barrier is complete, forming a bar, sea water may enter only 
at times of high tide or storm. Eventually evaporation will 
so concentrate the solution in the bay as to cause the pre- 
cipitation of sodium chloride and other salts. So long as 
these conditions lasted, salt would be precipitated, but beds 
of clayey material would be deposited wherever fine-grained 
sediment was supplied from the land. 

As will be seen by reference to the sea-water analyses 
given above, there are other salts present besides sodium 
chloride, and these will separate out in order of their 
solubilities, the least soluble ones being precipitated first. 
The order of precipitation would therefore be : (1) small 
amounts of lime carbonate and some hydrous iron oxide; 
(2) most of the sulphate of lime present ; (3) a mixture of 
sodium chloride and lime sulphate ; (4) sodium chloride of 
high purity ; (5) a mixture of sodium chloride and soluble 
salts of magnesia, potash, bromine, and iodine. 

This accounts for the frequent association of gypsum with 
salt ; but the potash and magnesia salts, precipitated last, are 
rare, because even after being precipitated they may, owing 
to their easy solubility, be removed by an influx of fresh 
water or by leaching of the deposit. The only locality 
where the complete series is found is at Stassfurt, 
Prussia. 



SALINES 127 

This deposit, which is of Permian age, is one of the most interesting 
in the world. It shows the following section : at the bottom is the 
main bed of rock salt which is broken up into layers 2 to 5 inches thick 
by layers of anhydrite. Above this comes 200 feet of rock salt, with 
which are mixed layers of magnesium chloride and poly halite (K 2 S0 4 , 
MgS0 4 , 2 CaS0 4 , 2 H 2 0). Resting on this is 180 feet of rock salt, with 
alternating layers of sulphates, chiefly kieserite, the sulphate of magnesia. 
These layers are about 1 foot thick. Lastly, and uppermost, is a 135- 
foot bed consisting of a series of reddish layers of rock salt and salts of 
magnesia and potassium, kainite (K 2 S0 4 , MgS0 4 , MgCl 2 , 6H 2 0), kieserite 
(MgS0 4 ), carnallite (KC1, MgCl 2 , 6H 2 0), tachhydrite (CaCl 2 , 2MgCl 2 , 
12H 2 0), as well as masses of snow-white boracite (Mg 7 Cl 2 B lc O 30 ). 

Natural Brines. — These, sometimes found in porous layers 
of the rocks, may result either from sea water imprisoned 
in the layers of sediment or from the solution of rock salt 
by percolating waters. 

Salt Marshes and Soils. — When away from the ocean, 
these owe their salinity to the infiltration of brine from 
neighboring saliferous formations. They sometimes repre- 
sent the site of former salt lakes. 

Distribution of Salt in the United States (Fig. 26). — In 
1903 most of the domestic production came from nine states, 
either in the form of artificial brine obtained by forcing 
water through wells to the salt, which is then brought up 
in solution, or else as rock salt, raised through shafts from 
underground workings. 

New York (13). — Salt was manufactured from brine springs 
at Onondaga Lake as early as in 1788 ; but the presence of 
rock-salt beds was not suspected until 1878, when a bed 
seventy feet thick was struck in drilling for petroleum in 



128 



ECONOMIC GEOLOGY OF THE UNITED STATES 



Wyoming County. Since then the development of the salt 
industry has been so rapid that for some years New York 
has been' one of the two leading salt-producing states. 

The salt occurs in lenticular masses interbedded with 
soft shales of the Salina series, which also carry gypsum 
deposits. The outcrop of the formation coincides approxi- 




Fig. 26. 



Map showing distribution of salt-producing areas in United States, 
compiled from various geological survey reports. 



mately with the line of the New York Central Railroad, 
but owing to its soluble character, no salt is found along 
the outcrops. The beds dip southward from 25 to 40 
feet per mile, so that the depth of the salt beneath the 
surface increases in this direction. 

At Ithaca, salt is struck at 2244 feet, and there are seven beds. The 
thickness of the individual beds varies, but the greatest known thickness 
is in a well near Tully, where 325 feet of solid salt was bored through. 
Though most of the New York product is obtained from artificial brines, 
a small quantity is mined by shafts. 



Plate XI 




Fig. 1. — Interior view of salt mine, Livonia, N.Y. Both roof and pillars are rock 

salt. 




Fig. 2. — Borax mine near Daggett, Calif. Photo, loaned by G. P. Merrill 



SALINES 129 

Michigan (11). — Salt in Michigan is obtained both from 
natural brines and from brines obtained by dissolving rock 
salt, as in New York. The natural brines occur in the 
sandstones of the Subcarboniferous, the most important 
locality being in the Saginaw Valley, where the brines are 
found in the Napoleon or Upper Marshall sandstone. They 
are remarkable for the large amount of bromine contained, 
more than half the bromine produced in the United States 
being obtained here. The vast beds of rock salt which 
occur in the Salina (Monroe) are exploited along the Detroit 
and St. Clair rivers and at Manistee and Ludington. The 
salt is dissolved by lake water pumped down and then re- 
evaporated, and soda ash (sodium carbonate) is made from 
the salt to a very great extent, by forced reaction with 
calcium carbonate. 1 

Other Eastern States. — In the Holston Valley of south- 
western Virginia salt is obtained by wells from the Lower 
Carboniferous shaly limestones. Part of the product is 
marketed as salt, and the balance is used in the manufacture 
of alkali (19). 

Brines are obtained from the Berea grit of eastern Ohio 
(14), and from those portions of Pennsylvania and West 
Virginia adjacent to the Ohio salt district. In the Kanawha 
Valley of West Virginia a natural brine is obtained by wells 
from the oil horizons. Brines are also present in the Car- 
boniferous of Illinois. 

Louisiana (8-10). — Brine occurs in springs and wells in 
the Cretaceous area of northern Louisiana, but the most 
important source of salt is in the extensive beds of rock salt 

1 Private communications from Dr. A. C. Lane, State Geologist of 
Michigan. 



130 ECONOMIC GEOLOGY OF THE UNITED STATES 

found in the southern portion of the state. These occur in 
a series of low knolls, called the Five Islands, beneath a 
series of clay, sand, and gravel beds. Though structural 
details are lacking, there seems in one case to be a dome 
fold and in Petite Anse a block fault. The age of the salt 
beds is Prepleistocene. Although the amount of rock salt 
present is evidently great, borings in one case having re- 
vealed a thickness of 1756 feet of solid salt, these deposits 
yield but a small percentage of the country's output. 

Kansas (7) . — Salt is found in this state under the follow- 
ing conditions : in the northern and central parts of the state 
as brine in salt marshes derived by leaching from the salifer- 
ous Dakota shales ; (2) a limited amount in eastern Kansas 
from wells sunk in the Carboniferous; (3) in the Permian 
of south central Kansas as beds of rock salt. At the present 
time the rock salt is the most important commercial source, 
being obtained in part as artificial brines and in part as 
rock salt. The thickness of the salt varies, the greatest 
aggregate thickness recorded in any well being 324 feet. 
The deposits thin out to the eastward, and the north and 
south limits are fairly well known, but the western boundary 
remains undefined. The absence of gypsum in close asso- 
ciation with the salt is a significant fact, but farther south 
it is found at a lower horizon, and the separation of the two 
is explained by a shifting sea bottom during deposition. 

Other Western States (16, 17). — Rock salt has been found 
at several localities in Texas, notably in Mitchell County 
and under the oil beds at Beaumont ; but none is yet pro- 
duced. In Utah, some salt is obtained by evaporating the 
waters of Great Salt Lake (18). In California the main 
supply of salt is obtained by evaporating sea water (6), an 



SALINES 



131 



elaborate system of ponds, covering thousands of acres, 
having been built on San Francisco Bay. These are filled 
at high tide, and the salt obtained by natural evaporation. 
A remarkable deposit of salt is worked at Salton Lake. 
This is a depression 27 miles long, 3J to 9 miles wide, and 
at its lowest point 280 feet below sea level. The deposit 
is formed by evaporation of the lake waters, which are fed 
by saline springs from the surrounding foothills. The salt, 
which has accumulated to a depth of 6 inches, is gathered by 
scrapers. Salt is also found in marshes, springs, or wells in 
a number of other localities in California (6). 

Analyses of Rock Salt from Various Localities 



Locality 



Retsof. N.Y. . . 
Pearl Creek, N.Y. 
Petite Anse, La. 
Saltville, Va. . 







- 




s 










^ H 


H 


t3 H 






~ A 


s a 


7 - 


a 5 


3 a 






o a 


S S 
o o 

►J >J 

< a 


w s 

h 

§5 


-< b 


I? 


tin 

<3 go — 


< 


98.701 


Tr. 


— 


.446 





.743 


Tr 


96.885 


.157 


.103 


.437 


— 


1.21 


1.21 


98.90 


.146 


.022 


.838 


— 


.014 


.08 


99.084 


Tr. 


— 


.446 


— 


.47 


— 



Authority 



F. E. Euglehardt 
F. E. Englekardt 
P. Collier 
C. B. Hayden 



Analyses of Solid Matter of Brines from Various Localities 




Extraction- — When salt forms underground deposits, it 
has to be extracted either by a process of solution or 



132 



ECONOMIC GEOLOGY OF THE UNITED STATES 



mining. In the former case water is forced down to the 
salt bed through a well, for the purpose of dissolving the 
salt, the brine being brought to the surface and evaporated, 
sometimes by solar heat, but more commonly by artificial 
means. In the latter case a shaft is sunk to the salt bed, 
and the material mined like coal and brought fco the sur- 
face in lumps, known as rock salt. Natural brines are 
pumped to the surface for evaporation. In the evapora- 
tion of brine care has to be taken to separate the gypsum 
and other soluble impurities present, which precipitate be- 
fore the salt does. 

Uses. — Salt is largely used in the meat-packing business 
and the manufacture of dairy products, as well as for 
domestic purposes. Therefore a number of different grades 
are called for, known under various names, such as table, 
dairy, common, fine, packers, solar, rock, milling, etc. Large 
quantities of salt are also consumed in the manufacture of 
soda ash, sodium carbonate, caustic soda, and other sodium 
salts. The chlorination of gold ores calls for an additional 
large amount. 

Production of Salt. — The increase in the amount of salt 
produced has been very marked, but it has been accom- 
panied by a decrease in price, as shown in the statistics 
given below : — 

Production of Salt in United States from 1880 to 1900 



Year 


Barrels 


Value 


Year 


Barrels 


Value 


1880 . . . 
1885 . . . 
1890 . . . 


5,961,060 
7,038,653 
8,876,991 


$4,828,566 
4,825,345 
4,752,286 


1895 . . 
1900 . . 


13,699,649 
20,869,342 


$4,423,084 
6,944,603 



SALINES 133 

Production of Salt by States from 1901 to 1903 





1901 


1902 


1903 




BAKKEL8 


Value 


Baeeels 


Value 


Barbels 


"Value 


New York . . 


7,286,320 


$2,089,834 


8,523,389 


81.938.539 


8.170.648 


$2,007,807 


Michigan . . 


7,729,641 


2,437,677 


8,131,781 


1,535,823 


4. 2! "7,542 


1,119,984 


Kansas . . . 


2,087,791 


614,365 


2,158,486 


514,401 


1,555,934 


564,232 


Ohio .... 


1,153,535 


455,924 


2,109,987 


593,504 


2,798.899 


795,897 


California . . 


601,659 


133,656 


682,660 


253,085 


029.701 


198,630 


Texas . . . 


(a) 


(a) 


347,906 


143,683 


314,000 


117,647 


West Virginia 


231,722 


94,732 


208,592 


97,721 


244,230 


35,797 


Utah . . . 


324,484 


326,016 


417,501 


270,626 


212,955 


181,710 


Louisiana . . 


(a) 


. (a) 


(a) 


(a) 


568,936 


178,342 


Other States . 


1,141,509 


465,245 


1,268,929 


321,254 


175,238 


86,942 


Total . . 


20,566,661 [$6,617,449 


23,849,231 


85,668,636 


18,968,089 


85.286,988 



(a) Included iu "Other States." 

The exports in 1903 were 16,446,380 barrels, valued at 
$70,296 ; while the imports for the same year amounted to 
132,143,546 barrels, valued at $564,966. 

World's Production of Salt ix 1902 



Country 



United States . 
United Kingdom 
France . . . 
Germany . . . 
Japan .... 
Italy .... 
Austria-Hun gary 
Russia .... 
Spain .... 
India .... 
Canada . . . 
Others . . . 

Total . . 



Short Tons 



3.839,891 
2,121,126 

982,479 (a) 
1,745,226 

761,575 (O 

505,401 

575,936 
1,913,696 0) 

470,057 

1,165,291 

63,056 

125,467 



13,769,201 



Value 



$5,668,636 
2.886,665 
2,605,800 (a) 
4,992,600 
4.159.245 (r/) 

711,400 
16,071,930 
2.767,168 0) 

707.424 
1,554.914 

288.581 

970,522 



$43,684,935 



(a) Includes Algeria. 

(d) Production and value, 1901. 

(e) Production and value, 1901. 



131 ECONOMIC GEOLOGY OF THE UNITED STATES 

REFERENCES ON SALT 

Technology and Origin. 1. Chatard, U. S. Geol. Surv., 7th Ann. 
Kept. : 491, 1888. 2. Englehardt, X. Y. State Museum, Bull. No. 
XI : 38, 1893. 3. Hubbard, Mich. Geol. Surv., V, Pt. II : 1, 1893. 
4. Ochsenius, Cheui. Zeit., XI: 1887. (Bar theory.) 5. Wilder, 
Jour. Geol., XI: 725, 1903. 

Areal. California: 6. Bailey, Calif. State Min. Bureau, Bull. XXIV: 
105, 1902. — Kansas: 7. Kirk and Haworth, Min. Resources of Kas., 
1898: 67. — Louisiana: 8. Lucas, Amer. Inst. Min. Engrs., Trans. 
XXIX : 462, 1900. (Rock salt.) 9. Yeatch, La. Exp. Sta., Pt. Y: 
209, 1899. (Rock salt.) 10. Yeatch, ibid., Pt. IY: 47, 1902. (X. 
La. salines.) — Michigan: 11. Lane, Mich. Geol. Surv., Ann. Rept., 
1901 : 241, 1902. — New Mexico: 12. Darton, U.S. Geol. Surv., Bull. 
260: 565, 1905. (Zuni.) — New York: 13. Merrill, N. Y. State 
Museum, Bull. XI, 1893. — Ohio: 14. Root, Ohio Geol., YI : 653, 
1888. — Oklahoma : 15. Gould, Kas. Acad. Soc, Trans. XYII : 181, 
1901. (Salt plains.) — Texas: 16. Cummins, Tex. Geol. Surv., 2d 
Ann. Rept.: 444, 1S90. (Northwestern Texas.) 17. Richardson, 
U. S. Geol. Surv., Bull. 260 : 572, 1905. (Trans-Pecos regions.) — 
Utah : 18. U. S. Geol. Surv., Min. Res., 1888: 605, 1890. — Virginia: 
19. Eckel, U. S. Geol. Surv., Bull. 213 : 407, 1903. (S. W. Ya.) 

BORAX 

Borax Minerals (3,4). — The chief minerals containing 
boron are borax, tincal, or sodium biborate, Na 2 B 4 7 , 
10 H 2 ; colemanite, Ca 2 B 6 O n , 5 H 2 ; ulexite, CaNaB 5 9 , 
8 H 2 ; boracite, 2 Mg 3 B 8 15 , MgCl 2 . These minerals are 
found usually as incrustations in alkaline marshes, or in 
lake waters of arid regions, or as bedded deposits. In 
some localities boric acid is found in fumarolic vapors. 

Distribution in United States (5). — Deposits of borax 
have up to the present time been discovered only in Cali- 
fornia (1, 2), Nevada, and Oregon. Borax was originally 
obtained by evaporation from the waters of Clear Lake, 
north of San Francisco, being produced in commercial 
quantities in 1864, and the solution was enriched by crys- 



SALINES 135 

talline borax obtained from the marshes surrounding the 
lake. This and other lakes of California were worked 
until the discovery of large deposits of nearly pure borax 
in alkaline marshes of eastern California and western Nevada 
in the early seventies. Several refining plants were located 
at these marshes, and the product was sometimes hauled a 
hundred miles to the railroad. Increased production and 
importation from Italy, however, reduced the price and 
caused these plants to be abandoned. 

The discovery, in 1890, that the marsh borax was a 
secondary deposit, derived from easily accessible and ex- 
tensive bedded deposits in the Tertiary lake beds of that 
region, revolutionized the industry. 

The most important of these beds is located near Daggett 
(PI. XI, Fig. 2), San Bernadino County, California, but 
much larger deposits are known in Death Valley. The 
borax, which forms a regular stratum, interbedded with 
sands and clays, is supposed by Campbell (2) to have been 
deposited in a series of Tertiary lakes, but the beds are 
in many instances tilted, due to violent crustal movements, 
which interrupted sedimentation at intervals. 

Uses. — The borax-bearing minerals are utilized chiefly 
for the manufacture of borax and boracic acid. Borax is 
used in industrial chemistry, in medicine, and as a labora- 
tory reagent. It is also employed in the assaying of gold 
and silver ores. 

Boric acid is used in the manufacture of borax, in colored 
glazes for decorating iron, steel, and metallic objects, in 
enamels and glazes for pottery, in making flint glass, as 
an antiseptic, and as a preservative for food. 



136 



ECONOMIC GEOLOGY OF THE UNITED STATES 



While several borax refineries are located on the Pacific 
coast, the main one is at Bayonne, New Jersey. 

Production of Borax. — The California colemanite de- 
posits form the main source of domestic supply, while small 
amounts are obtained from Nevada and Oregon. 

The United States production in 1903 was 34,430 short 
tons of crude borax, valued at 1661,400. The value of 
the refined product is naturally much higher, and its total 
value for 1903 would be $2,735,000. 

World's Production of Borax in 1902 



Country 



United States 
Bolivia . . 
Chile . . . 
India (1901) 
Germany 
Italy. . . 
Peru (1901) 
Turkey . . 



Quantity 
Metric Tons 



18,148 

593 

14,437 

162 

196 

2,763 

4,156 

9,000 



Mineral 



Calcium borate 
Calcium borate 
Calcium borate 
Borax 
Boracite 

Crude boric acid 
Calcium borate 
Pander mite 



REFERENCES ON BORAX 

1. Bailey, Calif. State Mining Bureau, Bull. 24: 33, 1902. (Calif, and 
general.) 2. Campbell, U. S. Geol. Surv., Bull. 200, 1902. (Calif.) 
3. Kemp, Min. Indus. I: 43, 1893. (General.) 4. Merrill, Non- 
Metallic Minerals: 313, N. Y., 1904. 5. Struthers, Mineral Census 
of 1902, Mines and Quarries : 885, 1905. (General.) 



SODIUM SULPHATE 



The hydrous sulphate, mirabilite or glaubersalt (Na 2 S0 4 
+ 10 H 2 0), is a white saline material, which is collected on or 
near the surface of some alkaline marshes in desert regions. 
It is known to occur at several localities in Wyoming. 



SALINES 137 

REFERENCES ON SODIUM SULPHATE 

1. Attfield, Jour. Soc. Chem. Ind., Jan. 31, 1895. 2. Knight, Min. 
Indus., Ill : 651, 1895. 3. Knight, Wyo. Agric. Exper. Sta., Bull. 
14, 1893. 

SODIUM CARBONATE 

Sodium carbonate, or natural soda, is obtained by the 
evaporation of the waters of alkali lakes, or is found as a 
deposit on or near the surface of alkaline marshes in arid re- 
gions. It is usually a mixture of sodium carbonate and 
bicarbonate in varying proportions, as well as impurities 
such as sodium chloride, sodium sulphate, borax, and sodium 
nitrate. 

Sodium carbonate is obtained from Owens Lake in Cali- 
fornia. An analysis of the waters by Chatard yielded : 
SiO 2 ,.220; Fe 2 3 , A1 2 3 , .038 ; CaC0 3 , .055; MgC0 8 ,.479; 
KC1, 3.137; NaCl, 29.415; Na 2 S0 4 , 11.080 ; Na 2 C0 3 , 26.963; 
NaHC0 3 , 5.725. The soda is purified by fractional dis- 
tillation. Soda is also known to occur in Oregon and 
Nevada. 

REFERENCES ON SODIUM CARBONATE 

1. Bailey, Calif. State Min. Bur., Bull. 24 : 95, 1902. 2. Chatard, U. S. 
Geol. Surv., Bull. 60 : 27, 1888. (Analyses.) 3. Russell, U. S. Geol. 
Surv., Mon. XI : 73. 

SODA NITER. 1 

Soda niter, or Chile saltpeter (NaN0 3 , with 63.5 per cent 
Na 2 5 when pure), is found in San Bernadino and Inyo 
counties, California, along the shore lines marking the 
boundary of Death Valley in Eocene times (1). It occurs 
in peculiar rounded hills of Eocene clay, the niter being 
found as a layer near the surface or distributed through the 

1 The term niter, when used alone, refers to potash niter. 



138 ECONOMIC GEOLOGY OF THE UNITED STATES 

clay. Very little soda niter is obtained from this source, 
and the main supply of this country continues to come 
from Chile, where extensive deposits are found in the 
desert region west of Iquique. There the niter (caliche) 
forms a bed 6 to 12 feet thick, under a cap of conglom- 
erate (costra) 1 to 18 feet thick. The origin of this deposit 
is interesting, and has caused considerable discussion. One 
theory quite generally accepted is that the niter was formed 
primarily by the slow oxidation in air of guano or other 
nitrogenous organic matter in contact with alkali ; a second 
theory refers its origin to the oxidation of organic mate- 
rials and ammonia, by microscopic organisms known as 
nitrifying germs. 

REFERENCES ON SODA NITER 

1. Bailey, Calif. State Min. Bur., Bull. 24 : 139, 1902. 



Plate XII 




Fig. 1. — Gypsum quarry, Alabaster, Mich. Shows gypsum overlain by glacial 
drift. The dump in foreground is overburden removed from gypsum. Photo., 
A. C. Lane. 




Fig. 2. —Rock phosphate mine near Ocala, Fla. Photo., A. W. Sheaf er 



CHAPTER VII 
GYPSUM 

Gypsum (1), the hydrous sulphate of lime (CaS0 4 , 2H 2 0), 
occurs most frequently in sedimentary rocks, interbedded 
with shales, sandstones, and limestones, and often more or 
less closely associated with rock salt. It is also, found as 
surface deposits of sand or mixed with clay (gypsite), as well 
as in limited quantities in volcanic regions, especially in lavas. 
When occurring in bedded deposits (PI. XII, Fig. 1) it is 
massive, of finely crystalline or earthy appearance, and of 
variable color, although most commonly white and gray. 
Transparent, colorless forms, known as selenite, are found as 
veins or crystals in the massive gypsum, or as plates and 
crystals in many clays, shales, and limestones. This variety 
by itself never forms deposits of commercial importance. 

Anhydrite differs from gypsum chemically in the absence 
of water, but changes to it on exposure to the air. 

Origin of Gypsum (3). — Gypsum is widely distributed 
both geographically and geologically, being found in vari- 
ous horizons from the Silurian to the Recent. Most beds 
of this substance have no doubt been formed by the evapo-. 
ration of salt water either in inland seas or else in arms 
of the ocean, the process of precipitation having been dis- 
cussed in the chapter on Salt. As gypsum separates from 
sea water after 37 per cent of the water has evaporated, 

139 



140 ECONOMIC GEOLOGY OF THE UNITED STATES 

while salt precipitates only after 93 per cent has been 
removed, it is evident that gypsum beds may be deposited 
without salt. This also explains why gypsum is more 
widely distributed than salt ; and the fact that the per- 
centage of gypsum in salt water is much less than that 
of salt probably accounts for its usual occurrence in the 
thinner deposits. 

Gypsum may also be formed by the decomposition of sulphides, 
such as pyrite, and the action of the sulphuric acid thus liberated on 
lime carbonate. Small quantities are formed in volcanic regions 
through the action of sulphuric vapors on the lime of volcanic tuffs 
or other rocks. 

G-ypsite, or gypsum dirt, is an earthy or sandy variety 
of gypsum forming a surface deposit in Kansas (9) and 
other western states (16, 19), which, in spite of its impure 
appearance, may run high in calcium sulphate. It is 
believed to be a deposit either in the soil or in shallow 
lakes supplied by springs whose water has dissolved the 
calcium sulphate from gypsum beds or other rocks. 
During its precipitation by the second method, its impure 
character is caused by its becoming mixed with clay or 
sand washed in from the land. 

Distribution in the United States (Fig. 27). — Eighteen 
states are producers of gypsum, although four of these — 
Iowa, Kansas, Michigan, and New York — supply most of 
the output of the country. 

Iowa (8) . — Important deposits are found in this state 
in an area of about 25 square miles in Webster County, 
especially near Fort Dodge. The gypsum, which is pre- 
sumably of Permian age, rests on the Coal Measures and 



GYPSUM 



141 



is covered by glacial drift. It varies from 3 to 30 feet in 
thickness, with an average of 16 feet, and much of it is 
sufficiently white for stucco. 

Kansas. — Gypsum (9) is found occurring either as rock 
gypsum, or as gypsite, the deposits forming a belt extend- 
ing across the central part of the state in a northeast- 
southwest direction, and includes three important areas. 




Fig. 27. — Map showing gypsum-producing localities of United States. After 
Adams, U. S. Geol. Surv., Bull. 223. 

The beds of rock gypsum are of Permian age, interbedded 
with red shales, those at the southern end of the belt being 
stratigraphically 1000 feet higher than those at the northern 
end. 

The gypsite or gypsum dirt, which is of more recent age, 
is found in the central area, as well as at a number of 
other localities. The spring waters which have supplied it 
have leached the calcium sulphate either from the gypsum 



142 ECONOMIC GEOLOGY OF THE UNITED STATES 

beds or the red shales. The product is used for fertilizer 
and cement plaster. 

Deposits of gypsum earth are found to the south of 
Kansas in Oklahoma (16) and northern Texas (16), as well 
as to the northwest in Wyoming (19, 20). 

Michigan (10) contains two important occurrences of gyp- 
sum, one in the vicinity of Grand Rapids, and the other at 
Alabaster on Saginaw Bay, both in beds of Lower Carbonif- 
erous age. That at Grand Rapids (PI. XII, Fig. 1) runs 
from 6 to 12 feet in thickness, forming several beds inter- 
stratified with shale and limestone. A third possibly pro- 
ductive area is near St. Ignace on the upper peninsula, where 
it occurs in the Salina. 

New York (11, 12). — Gypsum occurs in the Salina shales 
of central and west central New York. Most of the product 
is gray and used for land plaster ; but in recent years some 
whiter deposits, suitable for stucco, have been worked near 
Batavia. 

Other Occurrences. — Gypsum is also found in beds of 
Lower Carboniferous age in the Holston Valley of south- 
western Virginia (18). The rock is mined partly by under- 
ground workings, and some of the beds are fully 30 feet 
thick. The product is used for land and wall plaster. In 
Ohio gypsum has been obtained from the lower Helderberg 
beds of Ottawa County, 10 miles west of Sandusky. The 
material occurs at different horizons, the beds being bent 
into rolls, the main ones having a thickness of about 12 feet 
(13, 16). Additional occurrences are known in Wyoming 
(19, 20), Utah (17), Arizona (5), Nevada (16), California (6), 
Montana (16), Idaho (16), Colorado (7, 16), and South Da- 
kota (14-16). 



GYPSUM 



143 



Analyses. — The following analyses indicate the com- 
position of gypsum from different localities in the United 
States : — 

Analyses of Gypsum from United States 



CaO 



so 3 



H,0 



Insolu- 
ble 



CaC0 3 



A1 2 3 Fe 2 r »3 



MgO 



CO, 



Pure Gypsum . 

Onondaga, N.Y. 
Sandusky, 0. . 
Upper layer, 
Fort Dodge, la. 
Michigan . . . 
Medicine Lodge, 

Kas. . . . 
Gypsite, Salina, 

Kas. . . . 
Gypsite, Quanah, 

Tex. . . . 
Plasterco, Va. . 



32.60 46.50 



I 73.92 
32.35 46.38 



32.88 
32.53 
29.14 



78.44 
45.79 



45.73 
37.49 



78.66 
33.20 I 46.04 



20.90 



19.70 

20.76 
20.98 

20.46 

16.75 

8.49 
19.40 



4.64 
.91 

.65 



.19 

12.13 

7.43 
.10 



21.44 



5.07 



.10 

.99 

.12 
.70 



2.03 



Uses (1). — Gypsum is sold either in the ground, uncal- 
cined condition, or after calcining and screening. In the 
former state its chief value is as a fertilizer, it being marketed 
under the name of land plaster, which is also used as a dis- 
infectant. Though the softness of gypsum prevents its 
general employment as a building material, the pure white, 
massive varieties, known as alabaster, have been used for 
statuary, basins, vases, and other objects for interior decora- 
tion. Gypsum is also used to weight fertilizers, and as an 
absorbent of organic materials in them; as a flux in the 
manufacture of glass and porcelain; and, under the name 
of "terra alba" as an adulterant of foods and medicinal 
preparations. 



144 



ECONOMIC GEOLOGY OF THE UNITED STATES 



In its calcined form, gypsum is known as plaster of 
paris and has the following uses, dependent on its prop- 
erty of hardening or setting when mixed with water : 
stucco, plastering for walls, whitewash, pottery molds, 
statuary, and dental purposes, as a deodorizer, for crayons, 
and as a retarder of fermentation and absorbent of water 
in wines. 

Calcining Gypsum. — When heated to 250° C, gypsum loses a portion 
of its water of hydration, but if finely ground has the property of 
recombining with it. If heated to 300° C. to 400° C, it loses this power 
and is said to be dead-burned. In addition to dehydration, burning also 
breaks up the crystals into minute particles. The set is due to the for- 
mation of a crystalline network of the rehydrated grains. 

Since calcined gypsum sets in from 6 to 10 minutes, some retarding 
material, such as organic matter from slaughter-house refuse, is often 
added to it, and thus the setting process may be delayed from 2 to 6 
hours. Those plasters which set slowly are termed cement plasters. 

The following analyses show the composition of (1) uncalcined gyp- 
sum ; (2) the calcined rock ; and (3) the plaster after it has taken up 
water and set. From these it will be seen that the plaster takes up the 
amount of water lost in calcination. 



Series of Analyses showing Changes in Gypsum during 
Burning and after Setting 





Crude 


Finished 


Set 


Si0 2 and Insol. res 

Fe 2 3 and A1 2 3 

CaO 


12.29 
2.27 

29.67 
.78 

34.87 
3.52 

16.07 


14.31 
2.16 

33.53 
.91 

39.85 
4.11 
4.81 


12.03 

1.62 

30.05 


MgO 

S0 3 . . . . 

co 2 

H 9 


.61 

35.73 

3.55 

16.38 







GYPSUM 



145 



Production of Gypsum. — Michigan, New York, Iowa, and 
Kansas are the four leading producers, but many other states 
contribute small amounts as seen below. 

Production of Gypsum in United States from 1901-1903 





1901 


1902 


1903 




Short 
Tons 


Value 


Short 
Tons 


Value 


.Short 
Tons 


Value 


California, Ohio, 














and Virginia 


18,7861 


$49,344 1 


101,545 


$290,393 


103,392 


$467,113 


Colorado and 














Wyoming 


17,394 


76,435 


16,051 


73,372 


33,549 


133,347 


Iowa, Kansas, 














and Texas . 


213,419 


629,336 


295,769 


807,355 


307,102 


1,087,045 


Michigan . . 


185,150 


267,243 


240,227 


459,621 


269,093 


700,912 


New York . . 


119,565 


241,669 


110,364 


259,170 


137,886 


462,383 


Oklahoma . . 


15,930 


66,031 


34,156 


111,215 


69,158 


234,621 


Other states 


63,547 


176,583 


18,366 


88,215 


121,524 


707,522 


Total . . . 


633,791 


$1,506,641 


816,478 


$2,089,341 


1,041,704 


$3,792,943 



The imports for 1903 amounted to 269,484 short tons, 
valued at $468,597. 

World's Production of Gypsum, 1902 





Short Tons 


Value 


France 

United States 

Canada 

Great Britain 

Germany 

Algeria 


1,975,513 

816,478 

332,045 

251,629 

34,944 

6,889 

7,874 


$3,318,070 

2,089,341 

356,317 

384,263 

12,732 

52,253 

17,443 


Cyprus 




Total 2 


3,425,372 


$6,230,419 




1 Ohio, none reported. 

L 


2 India not 


available. 



146 ECONOMIC GEOLOGY OF THE UNITED STATES 



REFERENCES ON GYPSUM 

Properties and Technology. 1. Grimsley, Mich. Geol. Surv., IX, 
Pt. 2, 1903. 2. Grimsley and Bailey, Kas. Geol. Surv., V, 1899. 
3. Wilder, Eng. and Min. Jour., LXXIV: 276, 1902. 

Areal. 4. Adams and others, U. S. Geol. Surv., Bull. 223, 1904. 
(United States.) — Arizona: 5. Blake, Amer. Geol., XVIII: 394, 
1696. — California: 6. Crawford, Calif. State Mining Bureau, XII: 
503,1894. — Colorado: 7. Lee, Stone, XXI: 35, 1900. (Larimer Co.)— 
Iowa : 8. Wilder, la. Geol. Surv., XII : 99, 1902, and Jour. Geol., 
XI: 723, 1903. — Kansas : 9. Grimsley and Bailey, Kas. Univ. Geol. 
Surv., V, 1899. — Michigan: 10. Grimsley, Mich. Geol. Surv., IX, 
Pt. 2, 1903. — New York: 11. Merrill, N. Y. State Museum, Bull. 
11 : 70, 1893. 12. Parsons, N. Y. State Geologist, 20th Ann. Kept. : 
r 177, 1902. — Ohio: 13. Orton, Ohio Geol. Surv., VI: 696, 1888.— 
South Dakota: 14, U. S. Geol. Surv., Geol. Atlas Folios 85: 6. 
15. Todd, S. D. Geol. Surv., Bull. 3: 99, 1902. — United States: 16. 
Adams and others, U. S. Geol. Surv., Bull. 223, 1904. — Utah: 17. 
Boutwell, U. S. Geol. Surv., Bull. 225: 483, 1904. — Virginia : 

18. Eckel, U. S. Geol. Surv., Bull. 213: 406, 1903. — Wyoming : 

19. Knight, Wyo. Exper. Station, Bull. 14 : 189, 1893. 20. Slosson 
and Moody, Wyo. Coll. Agric. and Mech., 10th Ami. Kept., 1902. 



CHAPTER VIII 

FERTILIZERS 

Under this term are included a number of mineral sub- 
stances, limestone, marl, gypsum, phosphate of lime, green- 
sand, and guano, which are of value for adding to the soil to 
increase its supply of plant food. Since the first three of 
these have . other uses as well, they have already been dis- 
cussed in Chapters III, V, and VII. 

Phosphate of Lime. — This occurs both as crj^stalline phos- 
phate of lime, or apatite, and amorphous phosphate of lime, 
or rock phosphate. 

Apatite (5, 6). — This mineral, which theoretically contains 
42.3 per cent P 2 5 , is widely distributed in some igneous 
and metamorphic rocks, but rarely occurs in sufficient quan- 
tity, or in sufficiently concentrated masses, to render its 
extraction profitable, at least while the supply of amorphous 
phosphate lasts. No commercially valuable deposits have 
thus far been discovered in the United States; but in the 
provinces of Quebec and Ontario, Canada, apatite occurs in 
veins or pockets in metamorphic rocks, though little is now 
mined. 

Amorphous Phosphates. — These, though composed chiefly 
of phosphate of lime, also carry variable quantities of other 
substances. (See table, p. 154.) They occur (1) as con- 
cretionary bodies in consolidated rocks ; (2) as beds ; (3) as 

147 



148 



ECONOMIC GEOLOGY OP THE UNITED STATES 



irregular rocklike masses ; and (4) as nodular masses of 
varying size, often scattered through unconsolidated beds. 
As is shown in the following descriptions, amorphous phos- 
phates occur in various geological horizons, from the Silurian 
to Tertiary, and in several states in the Union, though 
most of the domestic supply comes from Florida, Tennessee, 
and South Carolina. 

Florida Phosphates (10). — This state is at present the 
most important phosphate producer, although the full extent 
and value of the deposits were unsuspected until the dis- 
covery of large beds along 
the Peace River in 1887. 
The phosphate deposits 
which are associated with 
Tertiary limestones of vari- 
ous horizons from the Eocene 
to the Pliocene form a curved 
belt, beginning west of the 
Appalachicola River and ex- 
tending east and then south 
through Dunnellon, and ap- 
proximately as far as Punta 
Gorda (Fig. 28). The to- 
pography varies from gently 
fig. 28. -Map of Florida phosphate rolling to flat pine lands and 

deposits. After Eldridge, Amer. Inst. <4wflmnv arpaq thp o-Pnpral 

Min.Eng., Trans. XXI: 197. swampy areas, tne general 

elevation being under 75 feet. 

Eldridge recognizes four types of phosphates in this area, 

viz. hard rock, soft rock, land pebble, and river pebble. Of 

these the hard rock phosphate (PI. XII, Fig. 2) is the richest, 

and has had most influence in the rapid development of the 




FERTILIZERS 149 

district. It is a hard, massive, close-textured rock, of vari- 
able color, and often containing irregular cavities which 
show a secondary deposition of phosphate. Accompanying 
this in some places is a second type, the soft phosphate, 
which is evidently a disintegration product. Bowlders of 
hard phosphate are frequently embedded in a matrix of soft 
phosphate, and also in sands and clays overlying the Eocene 
limestone. While the hard rock has an average of a little 
over 36.65 per cent of phosphoric acid, the soft phosphate 
rarely averages over 22.90. 

The land pebble or matrix rock is made up of pebbles of 
varying size, shape, and color, and composed either (1) of 
earthy material with fossils, quartz grains, and pisolitic 
grains of phosphate, or (2) of pebbles closely resembling 
the hard-rock phosphate. To render it marketable, the 
pebbles, which average 32.06 per cent phosphoric acid, have 
to be freed from the matrix by washing and screening. The 
unit composition of sale for land pebble is 68 per cent of the 
bone phosphate and 3 per cent of the combined oxides of 
iron and alumina, with moisture at 2 per cent. 

The river pebble consists of phosphate pebbles, having a 
blue, black, or dark gray surface, and mixed with sand, 
bones, and teeth. It is found in the present as well as in 
ancient river channels, in the latter case being covered by 
coastal sands. That found in the Peace River district 
averages 28.40 per cent phosphoric acid. 

All of the above-mentioned types, with the exception 
of the soft phosphates, are found underlying more or less 
separate regions (Fig. 28). 

The origin of the Florida phosphates has been a puzzling 
problem to geologists. Eldridge (10) has proposed two 



150 ECONOMIC GEOLOGY OF THE UNITED STATES 

theories : (1) that they have been derived by the leaching 
of guano and bone beds, and the deposition of the phosphate 
in the underlying limestone, either by precipitation in its 
pores or replacement of the lime carbonate ; (2) that they 
are due to the solution of the limestone and consequent 
concentrations of the less soluble phosphate of lime which 
was originally disseminated through the rock. Later solu- 
tions removed the limestones from around the phosphate 
deposits, leaving them as bowlders, which, at a still later 
date, were rounded by water currents which also deposited 
sand around them. 

The land pebble and river pebble probably represent 
nodules of a highly phosphatized marl, formed in limestone 
pebbles, shell casts, or by segregation of the contained lime 
phosphate, and subsequently set free by the solution of the 
lime carbonate. 

South Carolina Phosphates. — Phosphate is found both on 
the land and in the river bottoms in a belt about 60 miles 
long lying inland from Charleston and Beaufort (6, 17, 18). 
The phosphate, which rarely averages much over one foot in 
thickness, is commonly of nodular character, and often con- 
tains many bones and teeth. The presence of these animal 
remains, including both land and marine forms, has given 
rise to the belief that the deposits were caused by the accu- 
mulation of bones and excrements along a shore line, prob- 
ably of Upper Miocene age. Leaching of these remains 
may have permitted a later replacement of limestone or the 
formation of phosphatic concretions in swamp bottoms. 

Tennessee Phosphates (11,12,13,16,19). — Since the recogni- 
tion, in 1893, of considerable quantities of high-grade phos- 
phates in western middle Tennessee (Fig. 29), there have 



FERTILIZERS 



151 



been important developments of the deposits. Three types 
are recognized. The first is brown phosphate occurring in 
terraces along Duck River, Maury County. It is evidently 




Black Phosphate 



White Phosphate 



^ ^o a sp in haT e hi ^ y B b a e C Lnd ■ B — Ph0S ^ e 

Fig. 29. — Map of Tennessee phosphate areas. Compiled from data in U. S. Geol. 
Surv., Columbia Atlas folio, and papers by Hayes. 

derived from the weathering of near-by phosphatic limestone 
of Ordovician age. 

A second type, of black or blue color, occurs either in 
nodules or in beds. The bedded phosphate is underlain 



152 



ECONOMIC GEOLOGY OF THE UNITED STATES 



either by gray Devonian sandstone or by blue Silurian lime- 
stone, and capped by black carbonaceous shale ; the nodular 

form occurs higher 
up in the section. 
Both are believed 
to be chemical pre- 
cipitates on the 
floor of the Devo- 
nian sea. 

The third group 
includes white 
phosphates occur- 
ring in three con- 
ditions: stony, 
brecciated, and 
lamellar, inti- 
mately associated 
with Carbonifer- 
ous strata, but 
some occur in Si- 
lurian limestones. 
In the stony phase, 
the phosphate has 
been deposited in 
a siliceous lime- 
stone, replacing 
the lime. It al- 
ternates with beds 
of stony chert and 
contains under 50 
The brecciated form, which 




Fig. 30. — Vertical section showing geologic position 
of Tennessee phosphates. After Hayes. 



per cent of bone phosphate. 



FERTILIZERS 153 

is the most abundant, consists of angular chert fragments in 
a phosphate matrix deposited between chert fragments of a 
limestone. The lamellar variety was deposited in caverns 
in the Silurian limestones, which, since the deposition of the 
phosphate, has weathered to a residual clay in which the 
phosphate masses occur. 

Hayes has advanced the theory that the lime phosphate 
of the white phosphates was originally extracted from sea 
water by organisms, and accumulated on the bottom either 
as nodules or disseminated through the sediments. Later, 
when these strata were lifted above sea level and subjected 
to erosion and the action of percolating waters charged with 
acids from the soil, the phosphate was leached out and 
carried to lower levels where it was redeposited either in 
cavities or by replacing limestone. 

Other Phosphate Occurrences. — Phosphate, in the form of 
nodules, white vesicular rock, and in limestone fragments, 
occurs along the contact of Oriskany sandstone and Lower 
Helderberg limestone, in Juniata County, Pennsylvania (14). 
It contains 30 to 54 per cent bone phosphate. Nodular phos- 
phate, although not worked, is known to occur in Devonian 
strata in Arkansas (7), and in Cretaceous and Tertiary strata 
in Alabama (20), Georgia (15), and North Carolina (8). 

Composition. — The following analyses will serve to show 
the composition of some native phosphates. Of the impuri- 
ties present, lime carbonate is undesirable, since it neutral- 
izes the acid used in phosphate manufacture. Iron oxide, 
alumina, and silica are inert impurities displacing just so 
much phosphate of lime. 

The richness of a phosphate is usually expressed in terms 
of the tribasic-calcic phosphate, commonly termed bone 



154 



ECONOMIC GEOLOGY OF THE UNITED STATES 



phosphate. Of this about 45.80 per cent is phosphoric 

acid. 

Analyses of Phosphate Rock 





O 

2 


q 


c 




o 


6 
o 

03 

a 


►5 
o 


2 
O 

c 


o 

e3 

o 


is 


H 

H 1 
Z O 

o a 
- - 


►4 

CD 


Tennessee 


























Mt. Pleasant . . 


1.05 


34.69 


2.39 


3.36 


1.40 


3.18 


4.05 


2.64 


46.76 


1.39 


76.42 


s 


Swan Creek, 


























Hickman Co. . 


.50 


28.27 


3.14 


2.93 


1.15 




13.24 




40.50 






2.80 


White phosphate, 


























Stone Quarry 


























Hollow, Perry 


























Co 




15.30 








8.23 


54.88 




22.76 








Florida 
























MgO 

.30 


Hard rock . . . 


.07 


38.84 


.96 


3.07 


.65 




.49 


2.96 


50.08 


2.46 




Washed land peb- 
























.21 


ble 


.63 


34.72 


1.35 


2.53 


2.19 




4.34 


2.72 


47.95 


3.15 




44 


River pebble . . 


.56 


28.33 


1.05 


2.01 


3.99 




12.23 


4.90 


42.75 


2.44 






South Carolina 


























Average, S. C. 


























Analysis . . . 


3.68 


25.61 






4.68 




11.55 


4.78 






55.91 





Uses. — Fertilizers are used either in their raw condition 
or after undergoing proper preparation. Lime carbonate is 
commonly calcined before being spread on the soil, while 
gypsum is first pulverized before being sold as land plaster. 

Phosphate rock is treated with sulphuric acid to produce superphos- 
phate or acid phosphate, aud in this treatment ammoniates, or potash, or 
both, are sometimes added to the material. Concentrated phosphate is 
made by treating the phosphate rock with enough sulphuric acid to 
entirely decompose it, converting all the lime into sulphate, the phos- 
phoric acid solution being drawn off and further treated with additional 
quantities of high-grade phosphate. Since this form of phosphate there- 
fore requires raw materials of a high grade, and is much more exten- 
sively manufactured in Europe than in the United States, most of the 
high-grade Florida rock is exported. 



FERTILIZERS 155 

Guano. — Under this name are included surface deposits 
of excrement, chiefly of birds. Penrose (25) recognizes two 
classes : (1) soluble guano, of recent origin, which still con- 
tains most of its soluble ingredients; (2) leached guano, 
which has lost its soluble constituents by the action of rain 
or sea water. Most of the soluble guano of commerce was 
formerly obtained from Peru, where, it is said, the Incas, as 
well as the early Spaniards, valued it so highly that a death 
penalty was imposed for killing the birds which produced it. 
These deposits, from which many thousand tons have been 
obtained, are now exhausted. No large deposits of bird 
guano are known in the United States. Leached guanos occur 
on islands in the southern Pacific and in the West Indies. 

Bat guano has been found in the caves of Kentucky, 
Texas (26), and many other states, but few of the deposits 
have proved large enough to work, and none are of great 
extent, although one cave in Texas was known to yield 
1000 tons. The following analysis is representative : am- 
monia, 9.44 per cent; available phosphoric acid, 3.17 per 
cent; potash, 1.32 per cent. 

Greensand. — This term is applied to beds of marine 
origin, made up in large part of the green sandy grains of 
glauconite, the hydrated silicate of iron and potash. It 
also contains small amounts of phosphoric acid. Green- 
sands (23) are found at many localities in the Cretaceous 
and Tertiary formations of the Atlantic Coastal Plain, but 
New Jersey (22) and Virginia are the two important pro- 
ducers. The New Jersey greensand is spread on the soil 
in its raw condition, but that from Virginia is dried and 
ground for use in commercial fertilizers. 



156 



ECONOMIC GEOLOGY OF THE UNITED STATES 



The following analyses show its variable composition, and 
the comparatively small amount of P 2 5 and K 2 neces- 
sary to make it of value as a fertilizer. 

Analyses of Greenland 





p 2 o 5 


S0 3 


Si0 2 


C0 2 


K 2 


Na 2 


CaO 


MgO 


A1 2 3 


Fe 2 3 


H 2 


Pemberton, 
























N. J. . . . 


1.02 


.27 


50.23 


— 


6.32 


1.59 


1.40 


3.45 


7.94 


20.14 


9.00 


Aquia Creek, 
























Va. . . . 


.09 


— 


21.58 


29.79 


.37 


.59 


36.78 


1.05 


7.70 




.76 



Production of Fertilizers. — The production of phos- 
phate in the United States for several years was as 
follows : — 





1901 


1902 


1903 




Long Tons 


Value 


Long Tons 


Value 


Long Tons 


Value 


Florida . . 
South 

Carolina . 
Tennessee . 
Others . . 


751,996 

321,181 

409,653 

893 


$3,159,473 

961,840 

1,192,090 

3,000 


785,430 

313,365 

390,799 

720 


$2,564,197 

919,725 
1,206,647 

2,875 


860,336 

258,540 

460,530 

2,125 


$2,986,824 

783,803 

1,543,567 

4,600 


Total . . 


1,483,723 


$5,316,403 


1,490,314 


$4,693,444 


1,581,576 


$5,319,294 



The imports of crude phosphates, guano, and fertilizers 
in 1903 were valued at $985,324. The world's production 
in 1902, exclusive of Norway and Russia, was 2,766,253 
metric tons, valued at $9,778,950. The production of gyp- 
sum is given under that head. Greensand statistics are 
not available. 



FERTILIZERS 157 



REFERENCES ON FERTILIZERS 

General. 1. Adams, Araer. Inst. Min. Engrs., Trans. XVIII: 649, 1890. 
(List of Commercial Phosphates.) 2. Davidson, Eng. and Min. Jour., 
LILT: 499, 1892. (Deep Sea Formations.) 3. Davidson, Amer. Inst. 
Min. Engrs., Trans. XXI : 139, 1893. (United States and Canada.) 
4. Matthew, X. Y. Acad. Sci., Trans. XII: 108, 1893. (Nodules 
of Cambrian.) — Apatite: 5. Ells, Can. Rec. Sci., VI: 213, 1895. 
(Canada.) 6. Penrose, U.S. Geol. Surv., Bull. 46, 1888. (General.) — 
Phosphates : 7. Branner, Amer. Inst. Min. Engrs., Trans. XXVI: 
580, 1807. (Arkansas.) 8. Carpenter, X. Ca. Agric. Exper. Station, 
Bull. 110, 1894. (North Carolina marls and phosphates.) 9. Eckel, 
U. S. Geol. Surv., Bull. 213 : 424, 1903. (Decatur County, Tenn.) 
10. Eldridge, Amer. Inst. Min. Engrs., Trans. XXI: 196, 1893. 
(Florida.) 11. Hayes, U. S. Geol. Surv., 21st Ann. Kept., Ill: 473, 
1901. 12. Also 17th Ann. Rept., II: 513, 1896. 13. Hayes, 16th Ann. 
Rept., IV: 610,1895. (Tennessee white phosphates.) 14. Ihlseng, 
U. S. Geol. Surv., 17th Ann. Rept, III. (ctd.) : 995, 1896. (Penn- 
sylvania.) 15. McCallie, Ga. Geol. Surv., Bull. 5-A, 1896. (Georgia.) 
16. Memminger, U. S. Geol. Surv., Min. Res., 1893: 709, 1894. 
(Tennessee.) 17. Penrose, U. S. Geol. Surv., Bull. 46, 1888. 
18. Reese, Amer. Jour. Sci. iii, XLIII : 402. 1892. (South Caro- 
lina.) 19. Phillips, Eng. and Min. Jour., LVII : 417, 1894. (Hick- 
man County, Tennessee.) 20. Smith, Ala. Geol. Sur., Bull. 2: 9, 
1892. (Alabama.) — Greexsaxd : 21. Clark and Martin, Md. Geol. 
Surv., Rept. on Eocene, 1901. (Maryland.) 22. Cook, Geol. of X. J., 
1868: 261, 1868. 23. Parsons, U. S. Geol. Surv., Min. Res., 1901: 
823, 1902. (General.) 24. Wilber, U. S. Geol. Surv., Min. Res., 
1882: 552, 1883. (United States.) — Guaxo : 25. Penrose, U. S. 
Geol. Surv., Bull. 46 : 117, 1898. 26. Phillips, Mines and Minerals, 
XXI : 440, 1901. (Texas Bat Guano.) 



CHAPTER IX 
ABRASIVES 

Introductory. — Under this heading are included natural 
products employed for abrasive purposes ; but brief refer- 
ence will also be made to some artificial compounds which 
come into serious competition with the natural ones. 

The natural abrasives may be divided into the three fol- 
lowing groups: (1) Those, like grindstones, whetstones, 
and buhrstones, which occur in the form of massive rock, 
and which can consequently be cut and manufactured 
directly into the desired shape ; (2) those, like garnet, 
emery, quartz, and corundum, which occur usually as 
grains in a rock or vein, and which have to be separated 
mechanically from the rock; and (3) those, like infusorial 
earth, quartz sand, and pumice dust, which occur in more 
or less unconsolidated condition. 

While some abrasive substances occur as constituents of 
veins, the great majority form a part of rocks of either 
sedimentary, igneous, or metamorphic origin. That they 
are widely distributed both geologically and geographically 
is shown in the following description of the individual 
groups, and the map (Fig. 31) : — 

Grindstones (2, 3). — These are made from sandstones of 
homogeneous texture and sufficient cementing material to 
hold the quartz grains together, but not enough to so fill 

158 



Plate XIII 




Fig. 1. — Grindstone quarry, Tippecanoe, Ohio. J. H. Pratt, photo. 




Fig. 2. — Corundum vein between peridotite and gneiss, Corundum Hill, Ga. 
After Pratt, U. S. Geol. Surv., Bull. 180. 



ABRASIVES 



159 



the pores as to make the rock wear smooth under use. 
Most of the grindstones produced in the United States are 
obtained from the Berea grit of Ohio (PI. XIII, Fig. 1) and 
Michigan, certain layers of which are highly prized for 
this purpose. 




Fig. 31. — Map showing distribution of abrasives in United States. 

Pulpstones, which have a diameter of -48 to 56 inches, a thickness 
of 16 to 26 inches, and a weight of 2300 to 4800 pounds, are a thicker 
variety of grindstone. They are used for grinding wood pulp in paper 
manufacture, and hence have to withstand continual exposure to hot 
water. On account of their superior quality, pulpstones from New- 
castle-upon-Tyne, England, supply most of the American demand ; but 
it is probable that certain beds of the Ohio sandstones will be found 
suited for this purpose (3). 

Whetstones, Oilstones (2, 3, 10, 11), etc. — The term "whet- 
stone " includes those stones used for sharpening tools, the 
term " oilstone " being often applied when oil is placed on 
the stone to prevent heating and clogging of the pores by 



160 ECONOMIC GEOLOGY OF THE UNITED STATES 

grains of steel. The stones used for making whetstones 
are either sedimentary or metamorphic in character, and 
include sandstone, quartzite, mica schist, and novaculite. 
The stone selected will naturally vary somewhat with the 
exact use to which it is to be put, but even texture and 
comparatively fine grain are essentials. A small amount 
of clayey matter adds to the fineness of grinding, but an 
excess lowers the abrasive efficiency of the stone. In the 
schists used, abrasive action is due to the grains of quartz, 
or sometimes garnet, which are embedded among the fine- 
grained scales of mica. 

Rocks suitable for whetstone manufacture are found in 
many states, especially east of the Mississippi (2, 3), bat, on 
account of keen competition and limited demand, only the 
better grades from the best-located deposits are employed. 
Most of the supply is therefore obtained from a few states, 
especially Arkansas, Indiana, Ohio, New York, Vermont, 
and New Hampshire. 

Among the whetstones quarried in the United States, the Hindostan 
or Orange stone of Indiana and the Deerlick oilstone of Ohio are much 
used for oilstones. Scythestones are made from schistose rock in Graf- 
ton County, New Hampshire, and Orleans County, Vermont. 

The novaculite, quarried in Garland and Saline counties, 
Arkansas (10), represents a unique type, much prized for 
high-grade oilstones for sharpening small tools, and in 
demand both at home and abroad. It is an extremely fine 
grained sandstone made up of finely fragmental quartz 
grains, visible under the microscope. The rock is chertlike 
in superficial appearance and has a conchoidal fracture. 
While the deposits, which are stratified, have a total thick- 
ness of over 500 feet, the commercial novaculite is found 



ABRASIVES 161 

only in thin beds varying from a few inches to 15 feet in 
thickness. The beds have a steep dip, and are cut by 
several series of joints, which greatly interfere with the 
extraction of large blocks, and sometimes even with small 
ones. There are also structural irregularities and almost 
invisible flaws, so that much waste is caused in quarrying 
the rock. The rock has been variously regarded as a meta- 
morphosed chert, a siliceous silt, or a silicified limestone. 

Buhrstones and Millstones (2, 3) are stones of large diame- 
ter used for grinding cereals, paint ores, cement rock, barite, 
fertilizers, etc. The American stones are either coarse sand- 
stone or quartz conglomerate, and are quarried at several 
points along the eastern side of the Appalachian Mountains 
from New York to North Carolina. The most important 
beds are in the Oneida conglomerate, which is quarried in 
the Shawangunk Mountains of eastern New York and far- 
ther south in Pennsylvania. Some is also quarried in 
North Carolina. 

Many buhrstones are imported from France, Belgium, and Germany. 
Those from the first two localities are hard, cellular rocks, consisting 
of a mixture of fine quartz particles and calcareous material ; but the 
German buhrstone is basaltic lava. 

Pumice and Volcanic Ash. — The term " pumice," as used 
in the geological sense, refers to the light spongy pieces of 
lava, whose peculiar texture is due to the rapid and violent 
escape of steam from the molten lava. It is put on the 
market either in lump form, or ground to powder, or in 
compressed cakes of the ground-up material. In the com- 
mercial sense the term "pumice" includes volcanic ash as 
well as true pumice. 



162 ECONOMIC GEOLOGY OF THE UNITED STATES 

Most of the pumice used in the United States is obtained from the 
island of Lipari, north of Sicily. The stone, after being freed from the 
volcanic ash with which it is mixed, is sorted according to color, weight, 
and size, before it is shipped to market. 

Deposits of volcanic ash are abundant in many western 
states, for example in Nebraska (12) and Utah (13), but 
owing to inaccessibility these materials cannot compete with 
Lipari pumice, which is imported as ballast, and sells in its 
prepared form for 2 to 1\ cents per pound. 

Infusorial Earth and Tripoli. — These include all porous 
siliceous earths, composed of organic fragments, such as 
infusoria or diatom tests, which have accumulated either 
on the ocean bottom or in ponds. Such deposits are quite 
common in the coastal plain area of Maryland, Virginia (8), 
Georgia and Alabama, where they form beds several feet in 
thickness, generally inter stratified with the Tertiary sands 
and clays. In New England and New York (7) infusorial 
earth is frequently found in swamps formed by the filling of 
ponds. A deposit of tripoli worked near Carthage, Missouri 
(9), differs from those mentioned above in being the re- 
sidual silica left by the leaching of an impure limestone. 
It makes an excellent substitute for infusorial earth as an 
abrasive. Infusorial earth is known in other parts of the 
country, for example, Nevada and California, but is worked 
only to a small extent. 

The largest and best-known deposits of infusorial earth are in north- 
ern Germany, where it is found from 15 to 18 feet below the surface, in 
a bed varying from 18 to 45 feet in thickness. This is exported to all 
parts of the world. 

Infusorial earth and tripoli are used chiefly for polishing 
powders and scouring soaps. The porous character of 



ABRASIVES 163 

infusorial earth also renders it valuable as an absorbent for 
nitroglycerine. As a nonconductor of heat it is of value for 
steam boiler packing, for wrapping steam pipes, and for fire- 
proof cement. The tripoli of Missouri is used for water niters. 

Crystalline Quartz (3). — Much of the vein quartz quarried 
in the United States is pulverized and put on the market 
under the name of tripoli. Considerable quartz sand is used 
by stone cutters as an abrasive in sawing stone, and a small 
quantity is employed in making sandpaper. 

Garnet (3). — Although this is a common mineral in many 
metamorphic rocks, and of some value as an abrasive, it is 
produced at but few localities. Most of the supply comes 
from North Carolina, but some is obtained in New York, 
Connecticut, and Tennessee. It is used in the manufacture 
of garnet paper, and sometimes as a substitute for corundum 
in the manufacture of emery wheels, for, although softer, it 
possesses the advantage of having a splintery fracture, which 
prevents it from wearing smooth. The price varies from $20 
to $60 per ton when cleaned for the market. 

Corundum and Emery (4, 5, 6) . — Corundum, the oxide of 
aluminum, is, next to diamond, the hardest abrasive known, 
having a hardness of 9. It varies slightly in hardness, and 
also in chemical composition, being rarely pure alumina ; it 
also shows variable behavior when heated, some forms 
crumbling when exposed to a high temperature. Such 
kinds are worthless for the manufacture of emery wheels, 
since it is necessary to fire these in order to fuse the clay 
cement used in their manufacture. Emery is a mechanical 
mixture of corundum and magnetite or hematite, and is 
much more abundant than corundum. Its efficiency as an 



164 



ECONOMIC GEOLOGY OF THE UNITED STATES 



r~ 



m 



*m 






Slfllill 



abrasive depends on the percentage of corundum which it 
contains. 

Most of the commercially valuable deposits of corundum 
have been found in the eastern United States, in a belt of 
basic magnesian rocks, extending from Massachusetts to 
Alabama. These rocks reach their greatest development 
in North Carolina (Fig. 31) and Georgia, and most of the 
corundum is found there, in veins on the border of a peri- 
dotite mass which has been intruded into the gneiss. It 

is believed that 
the corundum, 
which was one 
of the earliest 
minerals to crys- 
tallize out from 
the cooling peri- 
dotite, was con- 
centrated around 
the borders of 
the mass by con- 
vection currents. 
This zone of co- 
rundum sent off 
tongues toward the interior of the mass, and now that erosion 
has removed the main zone of corundum, these tongues remain 
as apparently separate veins within the peridotite (Fig. 32). 
The most important emery deposit is that at Chester, 
Massachusetts ; but some is also worked near Peekskill, 
New York. The emery of Chester occurs in a local widen- 
ing of a belt of amphibolite schists, and forms a vein 
traceable for nearly five miles. The emery -bearing vein 



-'cWdum,.', -,. 
I Gneiss ,. , - » 't\.' ' ' •_ 

■■m 



pi 

m 

m 






Fig. 32. — Section showing occurrence of corundum 
around border of dunite mass. After Pratt, U. S. 
Geol. Surv., Bull. 180: 16, 1901. 



ABRASIVES 



165 



varies in width from a few feet up to 10 or 12 feet, while 
the emery streak in it averages about 6 feet, it being 
bordered on both sides by chlorite seams. The emery is 
in pockets, but these are traceable by a small vein of chlorite. 
After mining, both corundum and emery need to be cleaned 
and concentrated by special mechanical processes. The 
chief use of this material is as an abrasive, and for this 
purpose it is used in the form of wheels and blocks, emery 
paper, and powder. 

Artificial Abrasives. — Several artificial abrasives are now much manu- 
factured. Prominent among these is Carborundum, which is produced 
by fusion in the electric furnace of a mixture of silica, coke, and saw- 
dust; the reaction being Si0 2 + 3 C = CSi + 2 CO. The sawdust is 
added to give porosity to the mixture. 

Artificial corundum or alundum, whose introduction is of more recent 
date, is made by fusing bauxite in the electric furnace. It is put on the 
market in the form of wheels, while carborundum is either made into 
wheels or sold in powdered form. 

Production of Abrasives. — The value of the abrasives pro- 
duced in the United States during the last three years, together 
with the imports and artificial abrasives, was as follows : — 



Kind of Abrasives 


1901 


1902 


1903 


Oilstones and scythestones . . 

Grindstones 

Buhrstones and millstones . . 
Pumice 


$158,300 

580,703 

57,179 

52,950 

41,500 

158,100 

146,040 


$221,762 

667,431 

59,808 

2,750 

53,224 

84,335 

132,820 

104,605 


$366,857 

721,446 

52,552 

2,665 


Infusorial earth and tripoli . . 

Crystalline quartz 

Garnet 


76,273 

76,908 

132,500 


Corundum and emery .... 


64,102 


Total 

Artificial abrasives 

Imports 


11,194,772 
383,386 
490,712 


$1,326,755 
390,245 
426.736 


$1,493,303 
493,815 
621,585 


Grand total 


$2,068,870 


ft 2, 143,736 


$2,608,603 



166 ECONOMIC GEOLOGY OF THE UNITED STATES 



REFERENCES ON ABRASIVES 

General. 1. King, Ga. Geol. Surv., Bull. 2 : 119, 1894. 2. Pratt, U. S. 
Geol. Surv., Min. Res., 1900: 787, 1901. 3. Pratt, Mineral Census, 
1902, Mines and Quarries: 876, 1905. — Corundum and Emery: 
4. Eckel, Mineral Industry, IX: 15, 1901. (N. Y. emery.) 5. King, 
Ga. Geol. Surv., Bull. 2 : 73, 1894. (Georgia corundum.) 6. Pratt, 
U. S. Geol. Surv., Bull. 180, 1901. (U. S. occurrence, mining and 
concentration.) — Tripoli and Diatomaceous Earth: 7. Cox, 
N. Y. Acad. Sci., Trans. XII : 219, 1893, and XIII : 98, 1894. (Diat. 
earth, N. Y.) 8. Michels, Science, 1 : 222, 1880. (Ya.) 9. Quimby, 
Mineral Industry, YI : 17, 1898. (Mo.) — Whetstones, Grind- 
stones, and Millstones :» 10. Griswold, Ark. Geol. Surv., Ann. 
Rept. 1890, III, 1892. (Ark. novaculite.) 11. Kindle, Ind. Dept. 
Geol. and Nat. Res., 20th Ann. Rep. : 329, 1896. (Ind.) — Pumice 
and Yolcanic Ash : 12. Barbour, Neb. Geol. Survey, I: 214, 1903. 
13. Merrill, Non-Metallic Minerals : 398, N. Y., 1904. 



CHAPTER X 
MINOR MINERALS — ASBESTOS 

Asbestos Minerals. — Two different minerals are mined 
and sold under this name, one a variety of amphibole, the 
other a fibrous variety of serpentine known as chrysotile. 
The first, which forms pockets or veins in gneissic or schis- 
tose rocks, is white, gray, or greenish white in color. Chryso- 
tile usually occurs in seams of varying width in serpentine 
rocks (Fig. 33), its color being greenish white, green, or 
yellow, and its luster silky. 

In both forms of asbestos the fibers are easily separated, 
but the amphibole variety often contains gritty impurities 
which are difficult to remove. The fibers of chrysotile are 
shorter than those of the amphibole asbestos, rarely exceed- 
ing 1\ inches in length, but they have greater strength. 
Since the amphibole asbestos can be mined more easily, it 
is cheaper than the chrysotile variety, which, nevertheless, 
is in greater demand because more constant in character and 
suited to more uses. The two varieties are equal in value 
as nonconductors of heat. 

Distribution. — Amphibole asbestos is found at a number 
of localities in the crystalline belt of the Appalachians, but 
at present Sail Mountain in White County, Georgia, is the 
only producer, although promising deposits are known in 
Polk County, North Carolina, and Bedford County, Virginia, 
and are worked occasionally. 

167 



168 



ECONOMIC GEOLOGY OF THE UNITED STATES 



The limited supply of chrysotile asbestos has naturally 
stimulated prospecting, and deposits of promise have been 
found in Vermont (4), Wyoming, California, Montana (8), 

and Arizona (9). 
The Vermont de- 
posits, discovered 
in 1900, occur in 
Lamoille and Or- 
leans County, oc- 
cupying a rather 
limited area in a 
large serpentine 
belt (4). Two 
types of chryso- 
tile are found, one 
forming branch- 
ing veins similar 
in character and 
quality to the 
Canadian fiber, 
the other, of inferior quality, occurring as short fibers on 
slickensided surfaces. 

The main supply of chrysotile used in the United States 
is obtained from Black Lake and Thetford, Quebec. The 
serpentine is blasted out and the lumps bearing chrysotile 
separated from the barren rock by hand picking. These 
are crushed and screened and the fibres then separated from 
the rock by air currents. It is stated that 100 tons of rock 
yields two tons of commercial asbestos (5, 8) . 

There has been some difficulty in explaining satisfactorily 
the origin of the chrysotile veins in serpentine, for we have 




Fig. 33. 



Asbestos vein in serpentine. Photo, by G. P. 
Merrill. 



MINOR MINERALS 169 

here two quite different forms of the same mineral. Pratt, 
in attempting to explain the origin of the vein filling, 
believes that the fissures represent contraction cracks formed 
around the edge of the serpentine mass while cooling, and 
which were then filled by aqueous solutions from which the 
chrysotile crystallized. Merrill, on the other hand, believes 
the fissures to have been caused by shrinkage incident to a 
partial dehydration of the rocks and subsequent filling by 
crystallization extending from the walls inward (6). 

Uses. — Asbestos is used in fireproof paints, boiler cover- 
ing, for packing in fire safes, and for other purposes where 
non-conductivity of heat is required. Chrysotile is also 
used in making fireproof rope, felt, tubes, cloth, boards, 
blocks, and other objects. Asbestic is a name given to 
short-fibered chrysotile mixed with serpentine. 

Production of Asbestos. — The production of asbestos for 
the last three years was as follows : — 



Year 


Short Tons 


Value 


1901 
1902 
1903 


747 
1005 

887 


$13,498 
16,200 
16,760 



The imports in 1903 were valued at $689,327. 

REFERENCES ON ASBESTOS 
1. Ells, Amer. Inst. Min. Engrs., XVIII: 320, 1890. (Ontario.) 
2. Jones, Asbestos and Asbestic : Their Properties, Occurrence, and 
Use (London), 1897. 3. Pratt, U. S. Geol. Surv., Min. Res., 1904. 

4. Kemp, U. S. Geol. Suit., Min. Res., 1900: 862, 1901. (Vt.) 

5. Merrill, National Museum Guide to Study of Non-metallic Min- 
erals, 305: 1901. (General.) 6. Merrill, Geol. Soc. Amer., Bull. 
XIV, 1904. (Origin.) 7. Pratt, U. S. Geol. Surv., Min. Res., 1901 : 
897, 1902. 8. Pratt, Mineral Census, 1902, Report on Mines and 
Quarries: 973, 1904. 



170 ECONOMIC GEOLOGY OF THE UNITED STATES 

BARITE 

Barite, the sulphate of barium, is abundant at many 
localities, and in a few places in sufficient quantity to be 
of commercial value. Its usual mode of occurrence is as a 
series of pockets or lenses, which conform to the dip of the 
inclosing rock, often limestones. Galena is a common asso- 
ciate. Deposits of commercial value are found in Connecti- 
cut, North Carolina, Tennessee, Virginia, and Missouri (2). 
At Evington, Virginia (3), where the mines have been worked 
since 1874, the barite forms lenticular pockets in limestone. 
The barite-bearing stratum has a total length of about 4 
miles and a width of 100 to 200 feet or more. The pockets 
dip from 20° to 30° to the east, and are sometimes separate 
or may be connected by thin stringers of barite. Limestone 
is associated with the Tennessee and Missouri deposits, but 
in North Carolina barite lenses 3 to 6 feet thick occur in a 
decomposed schist. 

The following analysis of barite from Fulton County, Pennsylvania, 
shows the impurities which it may contain: BaS0 4 , 95.22; Fe 2 3 , A1 2 3 , 
.38 ; Mn0 2 , .05 ; CaO, .59 ; MgO, .18 ; C0 2 , .65 ; H 2 0, .23 ; Si0 2 , 2.45. 

Uses. — Barite, which is pulverized, and sometimes puri- 
fied by washing, is used in the manufacture of paper, rubber, 
paints, and for coating canvas ham sacks. It is also used in 
pottery glazes and in the manufacture of barium hydroxide. 
Its white color and great weight (sp. gr. 4.3) make it of 
value as an adulterant of white lead. Lithophone paint is a 
mixture of barium sulphate (68 per cent), zinc oxide (7.28 
per cent), and zinc sulphide (24.85 per cent). 

Production. — The production of barite for several years 
has been as follows : — 



MINOR MINERALS 



171 



Production of Crude Barite in the United States from 
1901 to 1903 





1901 


1902 


1903 




Quantity 
Short 
tons 


Value 


Quantity- 
Short | Value 
tons 


Quantity 
Short 
tons 


Value 


Missouri . . 
North Carolina 
Tennessee . . 
Virginia . . 


20,950 
7,390(&) 
10,460 
20,950 


$73,814 
22,615 
30,155 
31,260 


31.334 

14,679 

3,255 

12,400 


$104,677 
44,130 
14,647 
39,700 


23,178 
6,835 

14,684(«) 
5,700 


$77,712 
21,347 
32,691 
20,400 


Total . . . 


49,070 


$157,844 


61,668 


$203,154 


50,397 


$152,150 



(a) Includes the small production of Kentucky. 
(6) Includes the small production of Georgia. 

The imports of crude barites in 1903 amounted to 7105 
pounds, valued at $22,777, while those of manufactured 
barites were 5716 pounds, valued at $48,726. 

REFERENCES ON BARITE 

1. McCallie, Ala. Indus, and Sci. Soc., Proc. V : 25, 1895. (Ala.) 2. Eng. 
and Min. Jour., LXXIII : 762, 1902. (Mo.) 3. Pratt, U. S. Geol. 
Surv., Min. Res., 1901 : 915, 1902. (General.) 



FLUORSPAR 

Fluorspar or fluorite (CaF 2 ), a widely distributed mineral 
of variable colors, including white, green, and purple, is com- 
monly found in veins, including limestones, sandstones, slates, 
and gneisses, but seems to favor metamorphic rocks. It is not 
an uncommon constituent of many igneous rocks, and enters 
into the composition of some minerals, such as apatite, cer- 



172 ECONOMIC GEOLOGY OF THE UNITED STATES 

tain micas and topaz. Fluorite has also been observed in con- 
nection with some volcanic outbursts. (See Cripple Creek, 
under Gold.) Calcite and galena are sometimes found in 
the same vein. Fluorite is also noted, though rarely in 
economic quantities, in the gangue of many metallic minerals, 
especially lead. 

Distribution in United States. — In the United States fluorite 
is found at a number of points in the Piedmont and Ap- 
palachian areas from Maine to Virginia, and is likewise noted 
in small amounts in many metalliferous veins of the West, 
but it is rarely found in the Mississippi Valley. In unaltered 
limestone it is exceedingly rare, and the only commercially 
important deposits found in this kind of rock are in areas of 
igneous intrusions. 

Until 1898 the mines of Hardin and Pope counties, Illi- 
nois, were the only domestic source (1), and this area con- 
tinues to be the most important producer. There the deposits 
fill fault fissures in Lower Carboniferous limestone or sand- 
stone. Dikes of mica peridotite and lamprophyre also occur 
in the district, but not in contact with the veins. These 
latter in some places attain a width of 45 feet and a proven 
depth of 200 feet. This great width is due partly to enlarge- 
ment of the fissure by solution, and partly to a replacement 
of the limestone walls. In the limestone footwall, the fluor- 
spar sometimes forms a solid mass from 2 to 12 feet thick, but 
that on the hanging wall is less pure. The vein filling is 
chiefly fluorite and calcite, while associated with these are 
smaller amounts of galena, sphalerite, and occasionally pyrite 
or chalcopyrite. It is significant that the galena is slightly 
argentiferous. 



MINOR MINERALS 173 

The origin of the fluorite is somewhat doubtful, but 
Bain (1) believes that it has probably been derived from 
heated waters of either meteoric or magmatic origin which 
leached the mineral from some large mass of low-lying 
igneous rocks of which the dikes are offshoots. These 
heated ascending solutions are thought to have carried 
fluosilicates of zinc, lead, copper, iron, barium, and calcium. 
The dissolved compounds were probably broken up by cold 
descending waters, which possibly also furnished the sulphur 
to combine with the metals. 

Fluorspar deposits are also known in Kentucky (5), Ten- 
nessee (6), and Arizona (6), in the latter state occurring as a 
common gangue mineral of the metalliferous veins in Yuma 
County. 

Uses. — Fluorspar was formerly used chiefly for making 
hydrofluoric acid, but not more than 5 to 10 per cent of the 
domestic product is now employed for this purpose, while in- 
creasing quantities are sold for the manufacture of opalescent 
glass. The greatest demand for it, however, is as a flux in 
iron manufacture, since it saves from 3 to 5 per cent more iron 
than limestone flux, reduces the sulphur and phosphorous 
contents, and increases the tensile strength of the metal. 
On account of its valuable reducing properties, it is also 
used in making spiegeleisen, in foundry work, and in cupola 
furnaces. One objection to the more widespread use of 
fluorspar as a flux has been its high cost as compared with 
limestone. 

Fluorspar is divided into 6 grades for the market, the first- 
grade lump bringing 114.40 per ton in 1903. 

The production of fluorspar for 1903 was as follows : — 



174 ECONOMIC GEOLOGY OF THE UNITED STATES 



Production of Fluorspar in United States in 1903 



State 



Arizona and Tennessee 
Kentucky .... 
Illinois 

Total. . . . 




Value 



$2,037 

153,960 

57,620 

$213,617 



REFERENCES ON FLUORSPAR 

1. Bain, U. S. Geol. Surv., Bull. 255, 1905. (111.) 2. Burk, Min. Ind., 
IX : 293, 1901. (Ky.) 3. Emmons, Amer. Inst. Min. Engrs., Trans. 
XXI: 51,1893. (111.) 4. Min. Indus., IX: 203, 1901. 5. Fohs, 
Min. Ind., XII : 131, 1904. (Ky.-Ill.) 6. Pratt, U. S. Geol. Surv., 
Min. Ees. 1901 : 879, 1902. (Gen.) 



FULLER'S EARTH 



Fuller's earth is a term applied to a claylike mate- 
rial which has the property of absorbing greasy sub- 
stances. It was first used for fulling cloth or fur and 
hence the name, but in more recent years it has been found 
of great value for the clarification of mineral and vege- 
table oils, being used with the former as a substitute for 
charcoal. 

While fuller's earth resembles clay superficially, it usually 
differs from it in having lower plasticity, and a higher per- 
centage of combined water as compared with the alumina 
contents. It is often, though not invariably, high in mag- 
nesia. In color, fracture, and texture, it varies considerably, 
and the only satisfactory way of determining its value is by 
a practical test. 



MINOR MINERALS 



175 



Fuller's earth is not confined to any particular formation, 
but the known deposits occur in sedimentary rocks ranging 
from the beginning of the Mesozoic up to the Pleistocene. 
In Gadsden County, Florida, and in Decatur County, 
Georgia (1, 3), it is obtained from the Upper Oligocene of the 
Tertiary, the former locality being the most important in the 
country. The earth from this region is used for bleaching 
mineral oils. 

Earth of at least fair quality has been found at other localities in 
the southern coastal plain district. Small quantities of fuller's earth 
are also produced in Arkansas, eastern Colorado, and central New York 
(2). The last-mentioned occurrence has been used for cleansing cloth and 
also in the manufacture of soap. It is known to occur in Xebra'ska, 
South Dakota (2), and Alabama. 

Before the development of the Florida deposits, in 1893, much fuller's 
earth was imported from England, and even now a considerable amount 
is imported for use by the refiners of cotton-seed oil, since it bleaches 
better than most of the American earth. 

The following analyses indicate the composition of Ameri- 
can fuller's earth, and to these are added some analyses of 
the English material, for purposes of comparison, although 
chemical composition is of little value as a guide to the 
quality of the material. 





Si0 2 


A1 2 3 


Fe. 2 3 


CaO 


MgO 


H 2 


Na 2 


K 2 


Moist. 


Quincy, Fla. . . . 
Decatur Co., Ga. . 
Fairburn, S. D. . . 
Sumter, S. C. . . 

Yellow earth. 
Woburn Sands, Eng. 


62.83 
67.46 
58.72 
74.20 

47.10 


10.35 

10.08 
16.90 
10.10 

16.27 


2.45 
2.49 

4.00 
1.80 

10.66 


2.43 
3.14 

4.06 
1.90 

2.63 


3.12 
4.09 
2.56 
2.10 

3.15 


7.72 
5.61 
8.10 
5.70 

5.73 


.20 


.74 


6.41 
6.41 
2.20 
2.50 

15.12 


2.11 

1.60 



176 



ECONOMIC GEOLOGY OF THE UNITED STATES 



Production of Fuller's Earth. — The domestic output has 
never been large, and much is still imported from England. 

Production of Fuller's Earth in United States 
from 1901 to 1903 





Short Tons 


Value 


1901 


14,112 

11,492 
20,693 


$96,835 

98,144 

190,277 


1902 


1903 





REFERENCES ON FULLER" S EARTH 



1. Ries, U. S. Geol. Surv., 17th Ann. Kept., Pt. Ill (conk): 876, 1896. 

2. Ries, Amer. Inst. Min. Engrs., Trans. XXXI : 333, 1897. (S. Dak.) 

3. Vaughan, U. S. Geol. Surv., Bull. 213 : 392, 1903. (Fla. and Ga.) 



GLASS SAND 

Glass sand is obtained from quartzose sands, sandstones, or 
quartzites, usually having at least 98 per cent of silica and 
a very low percentage of iron oxide, as seen from the analyses 
given below. When sand is employed, it is sometimes 
necessary to put it through a washing process in order to 
separate the impurities, while in the case of quartzite or sand- 
stone a preliminary crushing and screening are necessarj r . 
Clay is undesirable since it tends to cloud the glass, while 
iron oxide imparts an undesirable color; but this may be 
counteracted to some extent by the addition of arsenic. 

Sands for glass making are sometimes obtained from 
Pleistocene deposits, but those from the Tertiary and 
Cretaceous formations are of better quality. Quartz rock 
(sandstone and quartzite) is found at various localities in 
the Paleozoic strata. 



MINOR MINERALS 



177 



Much sand is obtained from Silurian sandstones in La Salle 
and Randall counties, Illinois (5), for use in the plate glass 
works at Chicago. In New Jersey there are extensive pits 
in the Tertiary, around Bridgeton (4), the material being 
used by the glass works of southern New Jersey and south- 
eastern Pennsylvania. Large pits are also opened in the 
Raritan formation of the Cretaceous along the Severn River in 
Maryland (5). Of the quartz rocks, the Cambrian quartzites 
in Berkshire County, Massachusetts (5), the Oriskany sand- 
stone of West Virginia, and those of Pennsylvania (7) are all 
of importance. In Iowa the St. Peters sandstone is used (2). 

The following analyses taken from several American lo- 
calities will serve to show the composition of the materials 
employed : — 



Locality 


Si0 2 


A1 2 8 


Fe 2 3 


CaO 


MgO 


Miscel- 
laneous 


Geological 
Age 


Ottawa, IU. . . 


99.45 




.30 


.13 


Tr 




Silurian 


Hanover, N. J. . 


97.705 


.755 


.150 


.955 


.442 




Tertiary 


Berkeley Springs, 












Moist. 




W. Va. . . . 


99.37 


.33 


.04 




.17 
Loss, etc. 


Oriskany 


Columbia, Pa. 


99.5044 


.1337 


.2998 




.062 


Oriskany 


Cheshire, Mass. . 


99.46 


.48 


.06 




Ignition 


Cambrian 


Lewiston, Pa. . . 


98.84 


.17 


.34 Tr 


Tr 


.23 
Loss, etc. 


Oriskany 


Clayton, la. . . 


98.85 


.46 


.095 .21 




.384 


Ordovician 



The total production of glass sand in 1903 is given by the 
United States Geological Survey as 823,044: short tons valued 
at $855,828, and came from twelve states. It is doubtful, 
however, whether all this was used in glass manufacture. 
Ohio is credited with being the largest producer and Illinois 
second. 



178 ECONOMIC GEOLOGY OF THE UNITED STATES 



REFERENCES ON GLASS SAND 

1. Broadhead, Mo. Geol. Surv., 1872: 289, 1873. (Mo.) 2. Calvin, 
la. Geol. Surv., I: 24, 1893. (la.) 3. Collett, Geol. and Nat. 
Hist. Surv. of Ind., 12th Ann. Rept. : 22, 1883. (Ind.) 4. Cook, 
Geology of New Jersey, 1868 : 690, 1868. (N. J.) 5. Coons, U. S. 
Geol. Surv., Min. Res., 1902 : 1007, 1903. (General.) 6. DeGroot, 
Calif. State Min. Bur., 9th Ann. Rept. : 324, 1890. (Calif.) 7. D'ln- 
villiers, Second Pa. Geol. Surv., F: 271 and 288, 1891. (Pa.) 
8. Fuller, Stone, XVIII : 1, 1898. (General.) 



GRAPHITE 

Graphite, or black lead as it is often termed popularly, is 
a form of carbon, and occurs in two forms, the crystalline 
and amorphous. The first type is commonly found in granular 
or foliated masses, while the latter lacks crystalline struc- 
ture and is often shaly in its character. On this account 
some carbonaceous schists which resemble the latter in 
appearance, but contain no graphite whatever, are put 
on the market under its name. Even the best grades of 
crystalline graphite are, however, never pure carbon, as 
the following analysis shows : — 





C 


Ash 


Volatile Matter 


Ceylon graphite . . . 


98.87 


.28 


.90 



Distribution of Graphite in United States. — Crystalline 
graphite is widely distributed in the United States, occur- 
ring in contact zones between igneous and sedimentary 
rocks, in metamorphosed rocks, etc., but the known de- 
posits of commercial value are few in number. Most of 
the domestic supply has been obtained from the mines 



MINOR MINERALS 179 

near Ticonderoga (3), Essex County, New York, where the 
mineral occurs in a gray quartzite, which is interbedded 
with garnetiferous and micaceous gneiss and a quartzite. 
The rock contains about 10 per cent graphite, but not 
more than 50 per cent of this is saved in the process of 
extraction or concentration. Crystalline graphite is also 
mined in Chester County, Pennsylvania, where it forms 
two layers from 4 to 6 feet thick in decomposed mica schist 
(2, 4). Deposits are also known in Alabama, Georgia, 
North Carolina, New Hampshire, and Montana (4), but none 
of the localities have been important producers. Amor- 
phous graphite occurs in Rhode Island (4) in metamor- 
phosed carboniferous rocks, and the locality has attracted 
attention for many years, but its production has been very 
irregular, due partly to the fact that most attempts to 
utilize it have been unsuccessful. The material is some- 
what scaly, but does not as a rule carry more than 55 per 
cent carbon, the balance being siliceous impurities. That 
produced in Michigan (4) and Wisconsin is simply car- 
bonaceous schist, containing no graphite whatever. 

Most of the graphite used in the United States is obtained from 
Ceylon, where it occurs as veins in granulite and associated with 
feldspar, rutile, pyrite, biotite, and calcite. Weinschenk believes these 
deposits to have been formed by the decomposition of vapors carry- 
ing carbonic oxide and cyanogen compounds. Styria, Bohemia, and 
Bavaria are also important foreign sources of supply. All of these 
localities supply the American market, but Ceylon is the most impor- 
tant source by far. 

Uses. — On account of its refractoriness and high heat 
conductivity, graphite is employed in the manufacture of 
crucibles, for which purpose it is mixed with clay and 



180 



ECONOMIC GEOLOGY OF THE UNITED STATES 



some sand. In addition it is employed for making stove 
polish, foundry facings, paint, lead pencils, lubricating 
powder, glazing, electrotyping, steam piping, etc. 

Graphite is also made artificially from anthracite coal, 
but its introduction has not seriously affected the market 
for the natural product. 

Crystalline graphite is put through a concentrating process before 
shipment to market. This is necessary in order to free it from the 
associated minerals. Both wet and dry methods of separation are 
employed, while more recently air separation has been tried with 
some success. 



Production of Graphite. — The domestic production of 
crystalline graphite does not form more than a small pro- 
portion of the entire consumption, and has shown but a 
slight increase, whereas the output of amorphous graphite 
has shown great expansion, as can be seen by the figures 
given below. 

Production of Graphite in United States from 1901 to 1903 





1901 


1902 


1903 


Amor- 
phous 


Crystalline 


Value of 
both 


Amor- 
phous 


Crystalline 


Value of 
both 


Amor- 
phous 


Crystalline 


Value of 
both 


Short 
tons 
809 


Lbs. 
3,967,612 


$167,714 


Short 
tons 
4,739 


Lbs. 
3,936,824 


$182,108 


Short 
tons 
16,591 


Lbs. 
4,538,155 


$225,554 





The exports in 1903 were valued at $ 133,651, while the 
imports were valued at 11,207,730. The total domestic 
consumption for that year was 37,758 short tons, valued 
at 11,598,589. 

The world's production in 1902 is given below : — 



MINOR MINERALS 
World's Production of Graphite in 1902 



181 



Metric Tons 


Value 


25,593 


$3,505,455 


29,527 


368,186 


6,085 


182,108 


5,023 


41,755 


9,210 


35,934 


994 


28,300 


580 


3,176 


63 


1,900 


150 


1,140 


4,648 


C&) 



Ceylon . . 

Austria . . 
United States 

Germany . 

Italy . . . 

Canada . . 

Mexico . . 

Sweden . . 

France . . 

India . . . 

Total . 



81,873 



$4,167,954 



(6) Statistics not available. 



REFERENCES ON GRAPHITE 



1. Downs, Iron Age, Apr. 19 to June 14, 1900. 2. Frazer, Amer. Inst. 
Min. Engrs., Trans. IX: 730, 1881. (Pa.) 3. Xason, N. Y. State 
Museum, Bull. 4: 12, 1888. (N. Y.) 4. See also various volumes 
of the Mineral Industry, especially XI : 343, 1902, and XII : 183, 1903. 



LITHOGRAPHIC STONE 

Lithographic stone (1, 3) is a very fine-grained, homo- 
geneous limestone, used for lithographic purposes. It may 
be either pure lime carbonate or magnesian limestone, but so 
far as known this difference in composition exerts no impor- 
tant influence on its physical character. The two following 
analyses will serve to indicate this difference in composi- 
tion, No. 1 being the standard Bavarian stone and No. 2 
the Brandenburg, Kentucky, rock : — 



Insoluble in HC1 



Soluble in HC1 



Si0 2 (AlFe) 2 3 

1. 1.15 .22 

2. 3.15 .45 



CaO 



A1 2 3 FeO MgO CaO Na 2 K 2 Moist. H 2 

Trace .23 .26 .56 53.80 .07 .23 
.09 .13 .31 6.75 44.76 .13 .41 



CO, 

.69 42.69 
.47 43.06 



182 ECONOMIC GEOLOGY OF THE UNITED STATES 

The physical character of the stone is of prime impor- 
tance, for in order to yield the best results it should be 
fine-grained, homogeneous, free from veins or cracks, of 
just sufficient porosity to absorb the grease holding the 
ink, and soft enough to permit its being carved with the 
engraver's tool. Owing to these strict requirements but 
few localities have produced good stone. Lithographic 
stone is not confined to any one geologic formation, and 
deposits have been reported from many states both east 
and west. Some of these appear to be of inferior quality, 
while others are too far from railroads. The most prom- 
ising developed deposit is that found at Brandenburg, Ken- 
tucky (2, 6), at which locality a bed of blue-gray stone 
three feet thick is quarried and used by some establish- 
ments in the south and southwest. Another bed of good 
quality has also been described from Iowa (1). 

The main source of the world's supply is obtained from the Jurassic 
limestone of the Solenhofen district in Bavaria (4), in which the quarries 
have been worked for a number of years, but the supply is said to be 
becoming unsatisfactory and unreliable. The stones are trimmed at the 
quarries, and sizes of 22 or 28 by 40 inches are in the greatest demand. 
From these they range up to sizes 40 by 60 inches. The best quality 
stones sell for 22 cents per pound. 

The domestic demand is not large, and it is probable 
that one or two well-developed and well-managed native 
quarries could no doubt satisfy it. 

The successful substitution of zinc or aluminum plates 
for certain classes of lithographic work is said to have had 
a noticeable influence on the demand for lithographic stone. 
Onyx has also, in some cases, been found to make a good 
substitute. 



MINOR MINERALS 183 

REFERENCES ON LITHOGRAPHIC STONES 

1. Hoen, la. Geol. Snrv., XIII : 339, 1902. (la. also general.) 2. Kiibel, 
Eng. and Min. Jour., LXXII: 668, 1901. (Ky.) 3. Kiibel, Min. 
Resources, U. S. Geol. Surv., 1900: 861, 1901. (Excellent general 
article.) 4. Merrill, Non-Metallic Minerals : 116, 1904. 5. Mo. 
Geol. Surv., Bull. 3: 38, 1890. (Mo.) 6. Ulrich, Eng. and Min. 
Jour., LXXIII : 895, 1902. (Ky.) 

LITHIUM 

The two minerals most commonly used as a source of 
lithium are lepidolite (KLi[Al(OH 1 F 2 )]Al(Si0 3 ) 3 ) and 
spodumene (Li0 2 , A1 2 3 , 4 Si0 2 ). The largest deposits of 
lepidolite at present known in the United States are found 
near Pala, California. Spodumene occurs in some quan- 
tities in the Black Hills of South Dakota and in Connecti- 
cut and Massachusetts, but none of these occurrences have 
yet been worked to supply lithium. 

In the last few years there has been a great demand for 
lithium minerals for use in the manufacture of lithium car- 
bonate. Since most of this substance now in use is made 
in Germany, nearly all the American mineral has been 
shipped to that country. The American supply of carbon- 
ate is imported from Germany, selling in New York for 
$4.20 a pound. The chief use of lithium salts is in the 
preparation of mineral waters. 

The production of lithium minerals in the United States 
in 1903 amounted to 1155 short tons, valued at $23,425. 

MAGNESITE 

This mineral (1), which is a carbonate of magnesium with 
47.6 per cent of magnesia, usually occurs as a decomposi- 
tion product in the form of irregular veins in serpentine, 
talcose schists, or other magnesian rocks. Its color is 



184 



ECONOMIC GEOLOGY OF THE UNITED STATES 



white or yellowish, and when massive it resembles unglazed 
porcelain, but is quite brittle. Most of the magnesite used 
in the United States is imported from Styria and Greece ; 
but some is obtained in California (3), where a commercially 
valuable deposit is known. 

Magnesite is employed in the preparation of magnesium 
salts and in the manufacture of paint and of paper. Since 
it is a nonconductor of heat, it finds extensive use for this 
purpose ; in fact, its most important use is as a refractory lin- 
ing for open-hearth furnaces and converters in the steel indus- 
try, and for the brick lining of rotary Portland cement kilns. 

The domestic production is obtained entirely from Cali- 
fornia, and has been as follows : — 

Production of Magnesite in United States from 1901 to 1903 





Year 


Quantity 
Short Tons 


Value 


1901 

1902 

1903 


3500 
2830 
3744 


$10,500 

8,490 

10,595 



The total value of crude and calcined magnesite imported 
in 1903 was $461,398. 

REFERENCES ON MAGNESITE 

1. Struthers, U. S. Geol. Surv., Min. Res., 1902 : 983, 1903. 2. Yale, Eng. 
and Min. Jour., LXXVIII : 292,1904. (Calif.) 3. Yale, U. S. Geol. 
Surv., Min. lies., 1903 : 1131, 1904. (Calif, and general.) 



MICA 

There are few minerals more widely distributed in crystal- 
line rocks than mica, and yet deposits of economic value 
are rare because the mica flakes are either too small, or too 



MINOR MINERALS 185 

intimately mixed with other minerals, for profitable extrac- 
tion. Only two of the several known varieties of mica, mus- 
covite (H 2 KAl 3 Si 3 12 ) and phlogopite (H 6 K 6 Mg 7 Al 2 (Si0 4 ) 7 , 
are of economic value, the former being more valuable than 
the latter. The commercial deposits are usually found in 
pegmatite veins, cutting granites, gneisses, and schists. In 
these veins, which are of variable width, the mica is asso- 
ciated with quartz and feldspar, being found in rough 
crystals, called blocks or books, and which are either dis- 
tributed evenly through the vein or collected near its sides. 
The best mica is obtained from the more coarsely crystalline 
rocks ; but the widest veins do not necessarily contain the 
largest blocks. As a rule the mica does not form more 
than 10 per cent of the vein, and usually not more than 10 
or 15 per cent of that mined can be cut into plates, the rest 
being classed as scrap mica. 

Mica has been mined in a number of states both east and 
west, and in 1902 seven states were producers, of which 
North Carolina was the most important. 

The use of mica for stove doors and chimneys is decreas- 
ing, but there is a growing demand for small sheets which 
can be stamped out into circular or rectanglar forms and 
used for insulating purposes in electrical apparatus. Scrap 
mica, obtained by trimming larger sheets, is ground for use 
in wall papers, lubricants, boiler coverings, etc. Micanite is 
sheet mica obtained by cementing small clear pieces of scrap 
together under pressure. The value of the sheet mica ranges 
from 2 cents to $3 per pound, depending on the size of the 
sheet. Scrap mica sells for $8 to $10 per ton, and after 
grinding for $40 to $60 per ton. 

The production of mica in 1903 amounted to 46,693 short 



186 ECONOMIC GEOLOGY OF THE UNITED STATES 

tons, valued at $ 59,118. Most of the supply is imported from 
Canada and India, and this in 1903 amounted to 2,251,856 
pounds, valued at 1466,332. 

REFERENCES ON MICA 

1. Fuller, Stone, XIX : 530, 1899. (Occurrences and uses.) 2. Hender- 
son, Eng. and Min. Jour., LV: 4, 1893. (General.) 3. Holmes, 
U. S. Geol. Surv., 20th Ann. Kept., VI (ctd.) : 691, 1899. (U. S. 
deposits.) 4. Hoskins, Min. Industry, X: 458, 1902. (N. H.) 
5. Pratt, Mineral Census 1902, Mines and Quarries: 1031, 1904. 
(General.) 

MINERAL PIGMENTS 

Under this head are included a number of mineral sub- 
stances which are used in the manufacture of paints (5). In 
most cases they are put through some form of preparation 
after mining, such as grinding or washing. Roasting is some- 
times resorted to for improving the color. 

The substances commonly used are iron oxides, barite, 
gypsum, slate, graphite, asbestos, and soapstone. 

Hematite. — Certain kinds of hematite, such as the 
Clinton ore (see Iron Ores), are ground and sold under 
the name of metallic paints, and much used for coating 
wooden surfaces and coloring mortar. The ores are some- 
times roasted before grinding to improve their color and 
durability. Although iron-ore deposits are widespread, 
and often of large size, the quantity of material suitable 
for metallic paint is small. The chief supply comes from 
Pennsylvania, Tennessee, and New York, and smaller 
amounts from a number of other states. 

Ochers (2, 6). — This name is applied to powdery limonite 
deposits or clays, which, in their natural state, contain suf- 
ficient ferric oxide or hydroxide to impart a bright red or 



MLNOR MINERALS 187 

yellowish-red tint to the mass. Ocher may occur as a 
residual product resulting from the decay of limestone, 
shale, or other rocks, as a replacement deposit, or as a sedi- 
mentary deposit. The last-mentioned form probably con- 
tains more clay. Ocher sometimes contains as much as 
50-75 per cent iron oxide (6), and often gritty impurities, 
which have to be removed by washing. Uniformity of 
color in the product is necessary. 

Ochers are classified according to shade of color, thus : 
yellow ocher is colored by hydrous iron oxide ; red ocher 
owes its color to ferric oxide, and hence can be produced 
by roasting yellow ocher ; brown ocher or umber is colored 
by manganese, and sienna is a yellowish-brown variety. 

The most extensive series of ocher deposits found in the 
United States is associated with the Cambro-Silurian strata 
of the Appalachians from Vermont to Alabama, the chief 
production coming from Pennsylvania and Georgia. Both 
umber and sienna are produced in small quantities in Illinois 
and Pennsylvania, and sienna in addition is obtained from 
New York. 

Few paints are more free from adulteration than ochers, 
for the reason that any adulterant that could be used is 
more costly than the ocher itself. 

Slate. — The refuse from slate quarries is sometimes 
ground and sold as a pigment. 

G-ypsum, 1 known also as terra alba or mineral white, is 
used to some extent as a pigment for printing wall paper. 

Barite} or barium sulphate, which is used as an adulter- 
ant of white lead, is purified after mining by grinding and 
washing. 
1 For mode of occurrence and distribution see these minerals, pp. 139 and 170. 



188 



ECONOMIC GEOLOGY OF THE UNITED STATES 



Asbestos 1 is used to some extent in paint manufacture 
for the so-called non-inflammable or fireproof paints, but the 
total quantity thus utilized is small. 

Graphite, 1 either natural or artificial, supplies a black 
pigment of permanent color, which, on account of its 
resistance to the atmosphere and ordinary chemicals, is of 
much value for coating oxidizable metals, such as iron and 
steel. 

Calcium carbonate, in the form of chalk, known commer- 
cially as whiting or paris white, is used as a pigment to alter 
the shade of other pigments and as a basis for whitewash. 

Other paints. — Paints sometimes classed as mineral paints 
are made from other crude minerals, as follows : zinc white 
from zinc ore ; white lead, red lead, and orange mineral 
from lead ; Venetian red from iron sulphate ; vermilion or 
artificial cinnabar from quicksilver; chrome yellow from 
chromite ; cobalt blue from cobaltite. 



Production of Mineral Paints in the United States from 
1901 to 1903 





1901 


1902 


1903 




Quantity 




Quantity 




Quantity 






Short 


Value 


Short 


Value 


Short 


Value 




Tons 




Tons 




Tons 




Ocher . . . 


16,711 


$177,779 


16,565 


$145,708 


12,524 


$111,625 


Umber . . . 


759 


11,326 


480 


11,236 1 
4,316 J 


666 


15,367 


Sienna . . . 


305 


9,304 


189 


Metallic paint 


15,915 


204,397 


19,020 


313,390 


25,103 


213,109 


Mortar color . 


9,346 


112,943 


8,355 


98,729 


10,863 


101,792 


Soapstone . . 


50 


350 


1,100 


2,200 








Slate .... 


4,865 


41,211 


4,071 


39,401 


7,106 


59,029 



For mode of occurrence and distribution see these minerals, pp. 167 and 178. 



MINOR MINERALS 189 

The imports of ochers in 1903 amounted to 9,960,334 
pounds, valued at 1100,447; of umber, 2,168,570 pounds, 
valued at $18,172 ; and of sienna, 1,875,369 pounds, valued 
at 128,570. France is the largest producer of oclier. 

REFERENCES ON MINERAL PAINTS 

1. Benjamin, U. S. Geol. Surv., Min. Res. 1886 : 702, 1887. 2. Hayes 
and Eckel, U. S. Geol. Surv., Bull. 213 : 427, 1903. (Georgia ocher.) 
3. Hill, 2d Pa. Geol. Surv., Kept, for 1896, IV: 1386, 1887. 4. Min- 
eral Industry, IV : 491, 1896, and VII : 532, 1899. 5. Struthers, 
Mineral Census, Rept. on Mines and Quarries, 1902 : 955. 1903. 
(General.) 6. Watson, Araer. Inst. Min. Engrs., Trans. XXXIV: 
643, 1904. (Georgia ocher and analyses.) 

MOLDING SAND 

Certain fine-grained sands and loams are employed in 
making molds for castings. Molding sand must be suf- 
ficiently fine grained and aluminous to permit molding into 
the required form ; strong enough to hold its shape ; re- 
sistant to heat ; and porous enough to permit the escape of 
gases, but not to admit the melted metal. An excess of 
clay is undesirable, as it causes the sand to shrink and bake 
when the metal is poured in it. Molding sands are obtained 
from surface deposits at many localities, especially in the 
states east of the Mississippi River. The analysis of one 
from Manchester, England, may serve as a type, it containing 
Si0 2 , 92.913; A1 2 3 , 5.85; Fe 2 3 , 1.249; CaO, trace. This 
high silica percentage accounts for its refractoriness, and its 
porosity is due to a low clay content. The mechanical 
composition of molding sands is probably as important, if 
not more so, as their chemical constitution, but it has been 
little investigated. Many thousands of tons of molding 
sand are used annually by foundrymen, but no statistics 



190 ECONOMIC GEOLOGY OF THE UNITED STATES 

have been collected. The region around Albany, New York, 
supplies enormous quantities of a fine-grained molding sand. 
Ohio, Kentucky, and New Jersey are also important pro- 
ducers. 

REFERENCES ON MOLDING SAND 

1. Eckel, N.Y. State Geologist, 21st Ann. Kept., 1901. 2. Merrill, U. S. 
National Museum, Guide to Study of Non-metallic Minerals : 474, 
1901. 3. Merrill, Eng. and Min. Jour., LXXVIII : 341, 1904. 
4. See also forthcoming reports, Wis. Geol. Surv. and Va. Geol. 
Surv. 



MONAZITE 

This mineral is an anhydrous phosphate of the rare 
earth metals, cerium, lanthanum, and didymium, but its 
economic value is due chiefly to the small amount of 
thoria which it contains. Although grains of it are found 
scattered through many granites and gneisses, still no oc- 
currences of this type are of any commercial value. The 
economically valuable deposits are all found in stream 
gravels, derived from the disintegration of monazite-bearing 
rocks. Monazite is usually light yellow to honey yellow, 
red, or brown in color, has a resinous luster, and a specific 
gravity of 4.64 to 5.3. Its gravity and color aid in its ready 
determination. 

In the United States deposits of monazite sand have been 
found in the granite and gneiss areas of North Carolina (2) 
and South Carolina (3), and these, together with deposits 
found in Brazil (1), supply nearly the entire world's demand. 
A small quantity is also obtained from southern Norway, as 
a by-product in feldspar mining. The following analyses 
indicate the composition of monazite : — 



MINOR MINERALS 191 

Analyses of Xorth Carolina Monazite 





P 2 5 


Ce 2 3 


La 2 3 


Th0 2 


Si0 2 


H 2 


Burke Co., N. C. . . 
Alexander Co., X. C. . 


29.28 
29.32 


31.28 
37.26 


30.88 
31.60 


6.49 
1.48 


1.40 
.32 


.20 
.17 





Uses. — Monazite is usually separated from the gravels by 
a washing process, and in addition magnetic separation has 
in some cases been employed to separate it from the asso- 
ciated garnet, magnetite, and quartz. 

The value of monazite lies in the incandescent properties 
of the oxides of the rare earths, cerium, lanthanum, didym- 
ium, and thorium, which it contains, and which are utilized 
in the manufacture of mantles for incandescent lights. 

Production of Monazite. — The production of monazite for 
several years was as follows : — 

Production of Monazite in the United States from 
1901 to 1903 





Year 


Quantity 


Value 


1901 

1902 

1903 


Pounds 

748,736 
802,000 
862,000 


$59,262 
64,160 
64,630 





This quantity represents washed sand containing 85 to 99 
per cent monazite. The crude sand brings from 2J to 6 
cents per pound, depending on the percentage of thoria 
it contains. 

REFERENCES ON MONAZITE 

1. Dennis, Min. Indus., VI : 487, 1898. (General). 2. Nitze, N. C. 
Geol. Surv., Bull. 9, 1895. 3. Pratt, U. S. Geol. Sttrv., Min. Res., 
1902 : 1003, 1903 ; and 1903 : 1161, 1904. (X. C. and S. C.) 



192 ECONOMIC GEOLOGY OF THE UNITED STATES 

PRECIOUS STONES 

The names gems and precious stones (1, 2) are applied 
to certain minerals, which on account of their rarity, as 
well as hardness, color, and luster are much prized for 
ornamental use. The hardness is of importance as in- 
fluencing their durability, while their color, luster, and 
even transparency affect their beauty. A distinction is 
sometimes made between the more valuable stones, or gems 
(such as diamond, ruby, sapphire, and emerald), and the less 
valuable, or precious, stones (such as amethyst, rock crystal, 
garnet, topaz, moonstone, opal, etc.). 

Most gems are found in unconsolidated surface deposits 
representing either residual material, or alluvium derived 
from it, and in the latter their concentration and preserva- 
tion is due to their weight and hardness. When found in 
solid rock, the metamorphic and igneous types are more 
often the source than the sedimentary ones. 

Many different minerals are used as gems (1, 2), but only 
a few of the important ones can be mentioned here, and 
the number of the more valuable kinds found in the United 
States is very limited (7, 8, 9). 

Diamond. — This mineral, which is the hardest of all 
known substances, is pure carbon, crystallizes in the iso- 
metric system, and has a specific gravity of 3.525. It occurs 
in many different colors, of which white is the commonest, 
and is found either in basic igneous rocks, or in alluvial 
gravels. 

The massive forms, known as bort or carbonado, have little 
or no cleavage, and are of value only as an abrasive. 

The greatest number of diamonds come from South Africa, 



MINOR MINERALS 193 

but other deposits of commercial value occur in India, Borneo, 
and Brazil. 

In the United States a few scattered diamonds have been 
found in the southern Alleghanies, California, Wisconsin, 
and Indiana, but they are all small (3, 4, 5, 7, 8, 9). 

Ruby. — A red, transparent variety of corundum (A1 2 3 ), 
having a hardness of 9 and a specific gravity of 4. The 
most valuable color in ruby is a deep, clear, carmine red. 
Rubies of large size are scarce, so that a three-carat stone of 
good color and flawless is worth several times as much as a 
diamond of the same size. The best ones come from Bur- 
ma. In the United States they have been found in the 
stream gravels of Macon County, North Carolina. Those 
found in Arizona and other Western states are not true rubies, 
but a variety of garnet (7, 8, 9). 

Sapphire is a blue, transparent variety of corundum 
(A1 2 3 ). It is of slightly greater hardness and specific 
gravity than the ruby, though of similar composition. 
Sapphires of good color and size are more common than 
rubies and cheaper. The best sapphires come from Siam. 
In the United States they have been found in the gravels of 
Cowee County, North Carolina, but Yogo Gulch, Montana, 
where they are found in an igneous dike, is now the main 
source of domestic supply. They range in weight from 
under one up to four or five carats (7, 9, 10) . 

Emerald. — This gem is a variety of beryl, essentially a 
glucinum aluminum silicate. Its hardness is 7.5 to 8, and 
its specific gravity 2.5 to 2.7. Its brilliant green color is 
attributed by some to chromium, by others to organic mat- 
ter. Brazil, Hindostan, Ceylon, and Siberia are all important 
sources. In the United States a few have been found in 



194 ECONOMIC GEOLOGY OF THE UNITED STATES 

western North Carolina (7, 9). Flawless emeralds are very 
rare, and equal in value to diamonds. 

Aquamarine and oriental cat's-eye are also varieties of 
beryl. Brazilian emerald is a green variety of tourmaline, 
and lithia emerald an emerald-green spodumene. 

Topaz. — This is a fluosilicate of alumina, crystallizing 
in the orthorhombic system, with a hardness of 8, specific 
gravity of 3.5, vitreous luster, and yellow, green, blue, red, 
or colorless. It occurs in gneiss or granite, as well as in 
other metamorphic or igneous rocks, and is associated with 
beryl, mica, tourmaline, etc. It is also found in alluvial de- 
posits. The best gem stones come from Ceylon, the Urals, 
and Brazil. In the United States they have been found in 
small quantities in Maine, Colorado, and California (7). 

Turquoise is a massive hydrated aluminum copper phos- 
phate, of waxy luster, blue to green color, and opaque. Its 
hardness is 6, and specific gravity 2.75. It usually occurs in 
streaks and patches in volcanic rocks. The best varieties 
are obtained from Persia, but it is also obtained from Asia 
Minor, Turkestan, and Siberia. In the United States tur- 
quoises are found in the Los Cerrillos Mountains near Santa 
Fe, New Mexico, and Turquoise Mountain, Arizona. 

It is interesting to note that turquoise was hardly known in 
the United States in 1890, but now the bulk of the world's sup- 
ply comes from the Southwestern states and territories (6, 7). 

Garnet. — Of the several varieties of garnet, three are well 
known as gem stones, viz., the precious garnet or alman- 
dite, Bohemian garnet or pyrope, and manganese garnet or 
spessartite. The first two are of deep crimson, the last of 
orange-red or light red-brown color. India is the main 
source of supply. All three varieties mentioned are found 



MIKOR MINERALS 195 

in the United States, but there is a regular production only 
of the pyrope from Arizona and New Mexico, and a purple- 
red garnet known as rhodonite from North Carolina (7, 9). 

Opal, which is hydrous silica chemically, is amorphous, 
with conchoidal fracture, yellow, red, green, or blue color, 
and often showing considerable iridescence. The varieties 
recognized are the precious opal, fire opal, girasol, and com- 
mon opal. The finest examples of precious opal are obtained 
from Hungary. Others are also found at Queretaro, Mexico, 
and in Oregon and Washington. The United States pro- 
duction is small, although it is thought that there are many 
scattered occurrences in the igneous rocks of Washington, 
Idaho, Oregon, California, Nevada, and Utah (7, 9). 

Other Precious Stones. — Among the other precious stones 

obtained in this country and their sources of supply may be 

mentioned : — 

Tourmaline Maine and California. 

Kunzite California. 

Californite California. 

Chlorastrolite Isle Royale. 

Fluorspar Illinois. 

Rock crystal California. 

Amethyst Scattered localities. 

Chrysoprase Oregon. 

Moss agate Wyoming. 

Production of Precious Stones. — The production of gems in 
the United States is not large, and for the last three years 
was as follows : — 

Year Value 

1901 $289,050 

1902 328,450 

1903 . 321,100 

The imports of diamonds and other precious stones in 
1903 were valued at $26,522,523. 



196 ECONOMIC GEOLOGY OF THE UNITED STATES 

REFERENCES ON PRECIOUS STONES 

1. Bauer, Edelsteinkunde. (Leipzig, 1896.) 2. Farrington, Gems and 
Gem Minerals. (Chicago, 1903.) 3. Hobbs, Amer. Geol., XIV : 31, 
1894. (Wis. diamonds.) 4. Hobbs, Min. Indus., IX: 301, 1900. 
5. Hobbs, Jour. Geol., VII : 375, 1899. (Wis.) 6. Johnson, Sch. of 
Mines Quart., XXIV : 493, 1903. (N. Mex. Turquoise.) 7. Kunz, 
Mineral Census, 1902, Mines and Quarries. (General on United 
States Gems.) 8. Kunz. See Chapters on Precious Stones in Min- 
eral Resources, issued annually by U. S. Geol. Surv. 9. Kunz, Gems 
and Precious Stones of X. Amer. (New York, 1890.) 10. Pratt, 
U. S. Geol. Surv., Bull. 180, 1901. (Sapphire.) 11. Reid, Eng. 
and Min. Jour., LXXV: 786, 1903. (Burro Mtn. Turquoise dist.) 
12. Streeter, Precious Stones and Gems (London), 1892. # 



SULPHUR AND PYRITE 

These two minerals are discussed in the same chapter 
because they both serve as sources of sulphur. 

Sulphur. — The occurrences of native sulphur are of two 
types (4) : (1) the Solfataric type and (2) the G-ypsum type. 

Solfataric Type. — Sulphur is often found in fissures of 
lava and tuff around many active and also extinct volcanic 
vents, being deposited by the oxidation of hydrogen sulphide, 
or by the sulphuretted hydrogen and sulphur dioxide, in the 
presence of moisture, yielding water and sulphur. Ferric 
chloride is sometimes deposited under the same conditions, 
and might, owing to its similar color, be at first mistaken 
for sulphur. 

Deposits of the solfataric type are rarely of commercial 
importance, but in foreign countries they are worked in 
Japan, and also in the crater of Popocatepetl, in Mexico. 

In the United States a deposit is known to exist in Beaver 
County, southwestern Utah (4, 5). The sulphur is found 
impregnating volcanic tuffs, sand (the product of decom- 



MINOR MINERALS 197 

position), or in the fissures in trachyte and carboniferous 
limestone. The deposit is said to be 30 feet thick and the 
deposition still continues. Small amounts are mined in 
Oregon and Nevada (l), but the output is irregular. 

Gypsum Type. — This is formed by the action of bitumi- 
nous matter on gypsum, the former having a reducing effect. 
It is, therefore, always found in sedimentary rocks, in which 
marls, limestones, and shales are prominent. 

The change involved is a reduction of the calcium sul- 
phate of the gypsum, to calcium sulphide, with the produc- 
tion also of carbon dioxide and water. The sulphide then, 
by reaction with the carbon dioxide of the air, and water, 
yields calcium carbonate, native sulphur, and hydrogen 
sulphide. 

This type of sulphur is often of great economic value, and 
deposits are found in a number of countries. The beds are 
mostly of Tertiary age, but Jurassic ones are also known. 

In the United States the richest and best known is found 
in southwestern Louisiana (6, 8). Here a bed of sulphur 
over 100 feet thick was discovered in boring for oil. It 
is underlain by gypsum and salt, and covered by 300 to 100 
feet of wet clay, quicksand, and gravel, which has presented 
great difficulties in all attempts to mine the material. Its 
extraction is now accomplished by means of superheated 
steam. 

Sicily is the most important source of supply for the United States. 
There the sulphur is found in veinlets and cavities in a cellular Miocene 
limestone, which underlies and overlies gypsum. The sulphur-bearing 
beds are generally from 3 to 10 feet thick, and vary in their thickness 
as well as dip, the latter being from 25° up to 70°. The percentage of 
sulphur varies from 8 to 25 per cent, the first figure representing the 



198 



ECONOMIC GEOLOGY OF THE UNITED STATES 



lowest economic limit. The mines contain more or less petroleum and 
bitumen, and sometimes even explosive gases, while barite and celestite 
are associated minerals. Owing to improper methods of mining there 
is much waste. 

Uses. — The most important use of sulphur is for the 
manufacture of sulphuric acid, but small quantities are also 
consumed in the manufacture of matches, for medicinal pur- 
poses, and in making gunpowder, fireworks, insecticides, 
for vulcanizing india rubber, etc. 

In recent years pyrite has largely replaced sulphur for 
the manufacture of sulphuric acid, and the increase in price 
of Sicilian sulphur has helped this. 

The greater portion of the world's supply of sulphur is 
obtained from Sicily, the United States consuming the 
largest amount. 

Production of Sulphur. — The value of the domestic pro- 
duction and imports of sulphur for several years, as well 
as total domestic consumption, which includes sulphur 
obtained from pyrite, are given in the following table : — 

Imports and Production of Sulphur in the United States 





Domestic 
Production 


Imports 


Total 
Consumption 


1893 

1895 

1900 

1901 


Long tons 

1,071 
1,607 
3,147 

6,806 


Long tons 

105,823 
122,096 
167,696 
175,210 


Long tons 

228,709 
254,196 

408,038 
469,415 



The sulphur imported into the United States comes 
chiefly from Sicily and Japan, with very small quantities 
from Mexico and Chile. 



MINOR MINERALS 199 

REFERENCES ON SULPHUR 

1. Adams, U. S. Geol. Surv., Bull. 225: 497, 1904. (Xevada.) 2. Eng. 
and Min. Jour., XLVI: 174, 1888. (Sicily.) 3. Eng. and Mm. 
Jour.,LXXVII: 523,1904. (Sicily.) 4. Kemp, Min. Indus., II : 585, 
1894. (General.) 5. Russell, Trans., X. Y. Acad. Sci., 1 : 168, 1882. 
(Utah and Xevada.) 6. Preussner, Zeitschr. d. d. Geol. Gesell., 
XL: 194, 1888. (La.) 7. Richardson, U. S. Geol. Surv., BuU. 
260: 589, 1905. (El Paso Co., Tex.) 8. Anon., Eng. and Min. 
Jour., LXXVI1I: 592, 1904. (La.) 

Pyrite. — Pyrite, the sulphide of iron, is widely distrib- 
uted in nature, being found in many kinds of rocks and 
in all formations. It occurs in a variety of forms, such 
as disseminations, contact deposits, concretionary masses, 
fissure veins, and lenticular deposits, the last form being 
characteristic of most of those occurrences which are of 
commercial value. As mined, pyrite usually contains small 
quantities of other metallic minerals as well as silica and 
alumina ; but if its sulphur content falls below 50 per cent, 
it is not salable. The following analysis of pyrite from 
Louisa County, Virginia, will serve as illustration. It is : 
S, 47.76; Fe, 43.99; Cu, 3.69; Zn, .24; Si0 2 , 1.99; As, 
.63; Pb, .10. If chalcopyrite is present and exceeds 3 or 
4 per cent, the rock may be used as copper ore. Pyrrhotite 
is abundant in some of the Virginia deposits. 

Distribution. — The most important domestic occurrences 
are found in a belt of metamorphic rock extending from 
New Hampshire to Alabama (4), in which the pyrite is 
found forming lenses in metamorphic rocks. Massachusetts 
and Virginia are the most important producers. New York 
also contributes. In Louisa County, Virginia (2), the pyrite 
lenses occur in Cambro-Silurian slates and schists. The 



200 ECONOMIC GEOLOGY OF THE UNITED STATES 

deposits are known to be over 2 miles in length, and have 
been exploited to a depth of 600 feet, while their average 
thickness is 18 feet. Their origin is somewhat obscure 
and depends on the character of the original rock. 

Some pyrite is obtained from Indiana and Ohio, from 
"coal brasses" obtained as a by-product in coal mining (3). 

Uses. — Pyrite is used chiefly and in increasing quanti- 
ties for the manufacture of sulphuric acid and sulphate of 
iron, while small amounts are consumed in the manufac- 
ture of mineral paint. It is not used as an ore of iron. 
Recent experiments have demonstrated the possibility of 
saving the sulphuric acid gas from the roasting of zinc 
ores, and the utilization of pyrrhotite for making sulphur 
and sulphuric acid. 

REFERENCES ON PYRITE 

1. Adams, Trans. Amer. Inst. Min. Engrs., XII: 527, 1883. (Va.) 
2. Nason, Eng. and Min. Jour., LVII : 414, 1894. (Va.) 3. Struthers, 
Min. Indus., XI: 577, 1903. 4. Wendt, S. of M. Quart., VII: 218, 
1885. (Alleghanies.) 

STRONTIUM 

The two minerals serving as sources of strontium salts are 
celestite (SrS0 4 ) and strontianite (SrC0 3 ). Of these two 
the former is the more important, but the latter is the more 
valuable, as the strontium salts can be more easily extracted 
from it. 

Both celestite and strontianite have been found at a num- 
ber of localities in the United States, but seldom in large 
quantities. One important deposit of celestite has been 
found in limestone caves near Put in Bay, Strontian Island, 



MINOR MINERALS 201 

in Lake Erie, and in opening up the cave 150 tons of the 
mineral were taken out. Similar occurrences have been 
found in limestones in other states, but none of them have 
any commercial value. 

Nearly all the strontium salts now used in the United 
States are imported from Germany, the crude material being 
obtained in part from Westphalia, Germany, and also from 
Thuringia, Germany, and Sicily. 

Uses. — Strontium salts are used in sugar refining, in fire- 
works manufacture, and to a small extent in medicine. 

REFERENCES ON STRONTIUM 

1. Pratt, U. S. Geol. Surv., Min. Res., 1901 : 955, 1902. 

TALC AND SOAPSTONE 

Talc, a silicate of magnesia, is a widely distributed mineral, 
but rarely occurs in large quantities. It commonly repre- 
sents the alteration product of other magnesian minerals, 
such as tremolite, actinolite, pyroxene, or enstatite, and is 
therefore often associated with talcose or chlorite schists, 
serpentine, and such basic igneous rocks as peridotite. It is 
also found associated with dolomite. In the southern Ap- 
palachians the alteration of enstatite rocks into talcose rocks 
has given rise to extensive soapstone deposits, soapstone 
being an impure massive form of talc. 

Large deposits of pure talc, usually massive, though in 
places with a fibrous structure, are found in North Caro- 
lina (1). These beds, which are associated with marble and 
quartzite, have apparently been formed by the alteration of 
bands of tremolite bedded with the other rocks. Those 
portions discolored by iron oxide, or containing tremolite 



202 



ECONOMIC GEOLOGY OF THE UNITED STATES 



crystals, are of no value. A fibrous talc formed by the 
alteration of tremolite or enstatite occurs in St. Lawrence 
County, New York (3), where it is bedded with limestone 
and tremolite or enstatite schist. From these two regions 
most of the talc of the country is derived ; but soapstone is 
obtained from a number of states, of which Virginia is the 
most important producer. 

The following analyses from several localities show the 
kind and quantity of impurities which good talc may con- 
tain : — 

Analyses of Commercial Talc 



















H 2 


Locality 


Si0 2 


A1 2 3 


FeO 


CaO 


MgO 


Na 2 


K 2 


Loss on 
Igni- 
tion 


Kinsey Mine, 


















KC. . . 


.07 


1.56 


.67 


.30 


28.76 


.78 


Tr 


4.36 


St. Lawrence 














MnO 




Co.,N.Y. . 


62.10 




1.30 




32.40 




2.15 


2.05 



Uses. — Talc is marketed as rough talc, sawed slabs, or 
ground talc. Its peculiar physical character, extreme fine- 
ness, softness, and freedom from grit, adapt it to a number of 
uses, of which the following are most important: fireproof 
paints, electric insulators, foundry facings, boiler and steam- 
pipe coverings, soap adulterants, toilet powders, dynamite, 
in wall plasters, for dressing skins and leather, as a base for 
lubricants, and as a filling for paper. Most of the New 
York fibrous talc is used for the last purpose, being better 
suited for it than the North Carolina product. The com- 
pact varieties of pure talc are employed for pencils, and 
for coal- and acetylene-gas tips. 



MINOR MINERALS 



203 



Pyrophyllite differs from talc chemically, being a hydrous 
aluminum silicate, instead of a magnesium silicate, but when 
sufficiently free from grit it is put to the same use as talc. 
It is sometimes incorrectly called agalmatolite, because of 
its resemblance to the true mineral of that name. Deposits, 
more extensive than those of talc, are found near Glendon, 
North Carolina (1). It varies from green and yellowish 
white to white, but in all cases becomes nearly white when 
dried. 

Production of Talc and Soapstone. — The production for 
the last three years has been as follows : — 

Production of Talc and Soapstone from 1901 to 1903 





1901 


1902 


1903 




Short 
tons 


Value 


Short 

tons 


Value 


Short 

tuns 


Value 


New York (6) . . 

Georgia 

North Carolina . . 
N. Jersey and Pa. . 
Indiana and Virginia 
Other states (d) . . 


(59,200 
693 

5,819 

2.552(a) 
12,511 

7,068 


$483,600 

4,717 

77,824 

19,132(o) 

232,900 

90,315 


71,100 

(cj 

5,239 

7,082 
13,221 

1,312 


$615,350 
(c) 

88,962 

52,812 

372,1(13 

11,220 


60,230 
1,012 
5,330 
5,412 

13,118 
1,799 


$421,600 

9,042 

76,984 

44,058 

243,552 

44,824 



(a) Pennsylvania alone. (6) Fibrous talc, (c) California, Maryland, 
Massachusetts, New Hampshire, New Jersey, and Vermont in 1901 ; Cali- 
fornia, Massachusetts, and Georgia in 1902 ; California, Massachusetts, and 
Vermont in 1903. 

The imports in 1903 amounted to 1791 short tons, valued 
at $19,677. 

REFERENCES ON TALC AND SANDSTONE 

1. Pratt, N. C. Geol. Surv., Econ. Papers, No. 3, 1900. (N. Ca.) 2. Kand, 
Philadelphia Acad. Nat. Sci., Proc. 1894: 455. 3. Smyth, School 
of Mines Quart., XVII: 333, 1896. (N. Y. and bibliography.) 
4. Waldo, Mineral Industry, II : 603, 1894. 



CHAPTER XI 
MINERAL WATERS 

This term is commonly applied to those spring waters 
containing a variable amount of dissolved solid matter of 
such character as to make them of medicinal value. Their 
origin, although often regarded as curious, is simple, the 
dissolved substances having been derived from the rocks 
through which the spring waters have circulated. Many 
mineral waters contain carbonic and even other acids, and 
alkalies, which further increase their powers of solution. 
There is apparently some connection between hot mineral 
springs and geological structure, as they are more abundant 
in regions of faulting or recent volcanic activity. Mineral 
waters derived from sedimentary rocks usually show a 
greater quantity of dissolved material than those occur- 
ring in igneous rocks. 

Springs whose temperature is above 70° F. are termed 
thermal, those between 70° F. and 98° F. being classed as 
tepid, and those hotter than this as hot springs. The fol- 
lowing will serve as examples to show the temperature of 
different thermal springs : Sweet Springs, West Virginia, 
74° F. ; Warm Springs, French Broad River, Tennessee, 95°; 
Washita, Arkansas, 140° to 156°; San Bernardino Hot 
Springs, California, 108° to 172°; Las Vegas, New Mexico, 
110° to 140°. 

The volume of discharge shown by mineral springs is 

204 



MINERAL WATERS 205 

quite variable. The famous Orange Spring of Florida 
discharges 5,055,000 gallons per hour, while others are 
as follows : Champion Springs, Saratoga, New York, 2500 
gallons ; Roanoke Red Sulphur Springs, Virginia, 1278 gal- 
lons ; Warm Sulphur Springs, Bath, Virginia, 360,000 gal- 
lons ; Glen Springs, Waukesha, Wisconsin, 45,000 gallons. 

While a classification of mineral waters may be geo- 
graphic, geologic, therapeutic, or chemical, that prepared 
by A. C. Peale is perhaps as satisfactory as any. He sub- 
divides mineral waters into the following classes : — 

Alkaline 

Sulphated 



Alkaline-saline 

I Muriated 

^ . f Sulphated 

Saline . . . \ m r . 

I Muriated 

(Sulphated 
Muriated 
( Sulphated 
I Siliceous i 

I Muriated 

The springs falling in the above groups may be either 
thermal or non- thermal, and may be either free from gas 
or contain C0 2 , H 2 S, N, or CH 4 . 

Distribution of Mineral Waters in the United States. — 
There are, according to Peale, between eight and ten thou- 
sand mineral springs in the United States, and of this 
number 725 were producing in 1903. The majority of the 
commercially valuable mineral springs are located in the 
eastern United States and Mississippi Valley. West of 
the 101st meridian they are confined chiefly to the Pacific 
coast. No thermal springs are known in the New England 



206 



ECONOMIC GEOLOGY OF THE UNITED STATES 



states. Among the American springs, those at Saratoga, 
New York, have an international reputation, and compare 
well with many of the foreign ones. Others of importance 
are the Hot Springs of Virginia and the Hot Springs of 
Arkansas. 

The following table contains the analyses of several types 
of mineral waters from the United States : — 

Analyses of American Mineral Waters 









ao 






CO 










© 


A 




© 










% 


w 


©~ 


g 






Q 





3 


. % 


g 


'3 




Chemical Constituents 


ess Spring, 

TOGA, N. Y. 

Carbonate 


ior Spring, 
toga, N. Y. 
, Carbonat 


a, 

02 

M 

u 

S3 
02 2 


M © 
of <) 

S 3 


3 K 

a .* 3" 
5 * g " 
b 3 2 es 


:gas Hot Sp 
Mexico 
ine Saline 


© r 2 

CO SO 

^ w S 




5 < H 

* 52 S 

© m <S 


<d <; a 
H 3 5 

s«3 


S S 5 

< > i 


« 1 

© s 


"3$ 6 

C a W b 




S & s 

a < < 




Q 02 


J«3 00 


W H 


« <3 


^ <! 


PQ <! 




gr. per 


gr. per 


gr. per 


gr. per 


gr. per 


gr. per 


gr. per 




gal. 


gal. 


gal. 


gal. 


gal. 


gal. 


gal. 


Sodium carbonate .... 


— 


— 


— 


— 


— 


5.00 


— 


Sodium bicarbonate . 






10.77 


8.75 


— 


— 


.49 


— 


1.26 


Sodium sulphate . . 






— 


— 


— 


— 


— 


16.27 


.54 


Calcium carbonate . . 












5.22 


| 3.17 








Magnesium carbonate 






— 







— 


11.41 


— 


Calcium bicarbonate . 






143.40 


41.32 


— 


12.66 


12.93 


— 


17.02 


Magnesium bicarbonate 






121.76 


29.34 


— 


— 


.69 


— 


12.39 


Lithium bicarbonate . 






4.76 


— 


— 


— 


— 


Trace 


— 


Iron bicarbonate . . 






.34 


3.00 


— 


2.17 


— 


— 


.04 


Magnesium sulphate . 






— 


2.15 


— 


— 


18.96 


— 


— 


Potassium sulphate 






.89 


— 


1.38 


— 


— 


— 


— 


Sodium chloride . . 






400.44 


166.81 


— 


— 


.33 


27.34 


.46 


Potassium chloride 






8.05 












1.16 


Potassium bromide 






— 


1.57 












Sodium bromide . . 






8.56 














Sodium iodide . . . 






.14 


4.67 


— 


— 


— 


— 


— 


Silica 






.84 


.53 


1.72 


.38 


.45 


2.51 


.74 


Calcium sulphate . . 






— 


— 


14.53 


2.54 


96.64 


— 


— 



Production of Mineral Waters. — The production of 
mineral waters in the United States for the last three 
years was as follows : — 



MINERAL WATERS 



207 



Production of Mineral Waters in United States from 1901 

to 1903 



Year 


Quantity 
Gallons 


Value 


1901 ....... 


55,771,188 
64,859,451 
51,242,757 


$7,586,962 


1902 ... 


8,793,761 


1903 


9,041,078 







The production of the more important states in 1903 was 
as follows : — 

Production of Mineral Waters in Several States in 1903 



State 



New York . 
Wisconsin . 
California . 
Virginia . . 
Pennsylvania 



Quantity 
Gallons 



1,827,408 
1,293,777 
1,862,855 
2,561,502 
1,522,860 



Value 



$1,432,801 

1,058,954 

706,372 

477,410 

357,579 



REFERENCES ON MINERAL WATERS 

Bailey, Kas. Geol. Snrv., VII, 1902. (Kas.) 2. Branner, Ark. Geol. 
Surv., Rept. for 1901. (Ark.) 3. Crook, Mineral Waters of United 
States and their Therapeutic Value. (Phila., 1899.) 4. Lane, U. S. 
Geol. Surv., Water Supply Bull. XXXI, 1899. 5. Peale, U. S. Geol. 
Surv., 19th Ann. Rept., 1898. (U. S.) 6. Schweitzer, Mo. Geol. 
Surv., Ill, 1892. (Mo., also general.) 



UNDERGROUND WATERS 

While much of the water used for supplying towns and 
cities, for irrigation purposes, etc., is obtained from below 
the surface, all of it originates in rainfall. The rain water 
falling on the surface is disposed of in part by evaporation 
and surface run-off, but a variable and sometimes large per- 
centage seeps into the ground. 



208 ECONOMIC GEOLOGY OF THE UNITED STATES 

Ground Water (22). — Of this portion soaking into the 
ground, a small part is retained by capillarity in the surface 
soil, to be returned again to the atmosphere either by direct 
evaporation or through plants, but most of it finds its way 
into the deeper layers of the soil, which it completely 
saturates. 

The water in this saturated zone, which is termed the ground 
water, forms a great reservoir of supply for lakes, springs, and 
wells, and its upper surface, known as the water table, agrees 
somewhat closely with that of the land surface, but is nearer 




Fig. 34. — Ideal section across a river valley, showing the position of ground 
water and the undulations of the water table with reference to the surface 
of the ground and bed rock. After Schlichter, U. S. Geol. Surv., Water 
Supply Bull. 67: 1. 

to it under valleys, and farther from it under hills (Fig. 34). 
The depth of the water table is quite variable, being but a 
few feet below the surface in moist climates, while in arid 
regions it may be 100 feet or more. In any area, however, 
the water table may show periodical fluctuations. In all 
ground water there is a slow but constant movement from 
higher to lower levels, just as in the case of surface waters, 
so that the ground water flows towards the valleys. There 
it may discharge into the streams, but in some instances 
it follows the valley bottom below the river bed, separated 
from the river water by a more or less impervious layer (22). 
The composition of the ground water also shows a somewhat 
close relation to the rocks or soils in which it accumulates. 



MINERAL WATERS 209 

Artesian Water. — In some areas much of the water which 
percolates through the soil is caught up. by porous beds of 
sandstone, gravel, or in rarer instances limestone, and where 
these are between impervious beds such as shale, the absorbed 
water may follow them for some distance, especially if the 
porous stratum is inclined. Water thus confined is under 
pressure, and tends to rise towards the surface along any 
path of escape open to it, such as joint or fault planes, or 
where the water-bearing bed is cut into by a stream. A drill 
hole bored to tap the water-bearing bed serves the same pur- 
pose ; and when the pressure is sufficient to force the water 
upward so that it flows from the tube, it is called an arte- 
sian well. The term is however rather loosely used now and 
applied to many deep wells which are not flowing. 

The requisite conditions (1) for a supply of artesian water 
are : (1) a porous stratum ; (2) an impervious bed below and 
above the water-bearing bed •; (3) inclined beds, so that the 
point of intake or fountain head can be higher than the well; 
(4) a sufficient area of outcrop or collecting area to obtain a 
large enough supply — this may be many miles from the 
well; (5) adequate rainfall; (6) absence of escape for the 
water at a lower level than the surface at the well. Artesian 
water was formerly looked for only in synclinal basins, but 
it is now known that sedimentary beds may be water bear- 
ing in areas of monoclinal dip. 

Artesian wells vary greatly in their capacity and depth. 
Some are not more than 100 feet deep, while others are 2000 
or more feet deep. 

Though the most productive artesian wells are found in 
pre-Pleistocene sedimentary rocks of regular structure (Fig. 
35), still, flowing artesian wells even of large capacity are 



210 ECONOMIC GEOLOGY OF THE UNITED STATES 

at times found in the glacial drift where water-bearing 
lenses of sand or gravel are overlain or surrounded by 
clay. 

Even in areas of igneous and metamorphic rocks the water 
seeps in along joint planes, and collects at times in sufficient 
quantities to serve as a source of supply which may even be 
under pressure (6, paper by G. O. Smith). 






Atlantic Ocean 



^Delaware Bay ^ M &° 




Ch T a r ke •£ ** C^ ^fi ^ ^ 



T 




s^£=n 



mam ^^ 




.... . ^V" c^v^i <.-- sV ?^v >W " V ">° ,W Atlantic 


GRANITE. ETC. 






SCALES: Huiizonla 


1" 




\i,;„ 





Fig. 35. — Geologic section of Atlantic Coastal Plain, showing water-bearing 
horizons. After Barton, Amer. Inst. Min. Engrs., Trans. XXIV: 375. 

Artesian wells are to be distinguished from ground water 
wells by their greater constancy, absence of relation to sur- 
rounding climatic conditions, and, in moist climates at least, 
of a high constituent of mineral matter. 

There are many areas in the United States in which the 
conditions are favorable to an artesian water supply, as the 
various state and government reports will show. A few of 
the more important may be briefly referred to. 

Along the Atlantic and Gulf Coastal Plain an abundant 
supply of artesian water is obtained from the Cretaceous 
and Tertiary beds, at depths varying from 50 feet along 



MINERAL WATERS 211 

the inland border, to 1000 feet and over along the coast (4) 
(Fig. 35). 

A second area is that of the upper Mississippi Valley (19), 
in which an abundant supply of potable water is obtained 
from the St. Croix and St. Peters sandstone, whose outcrop 
in Minnesota and Wisconsin covers some 14,000 square miles. 

In the Great Plains (2) region water is obtained from the 
Dakota sandstone, whose collecting area is around the border 
of the Black Hills (Fig. 36). This source is available in 




Fig. 36. — Section from Black Hills across South Dakota, showing artesian well 
conditions. After Barton. 

South Dakota and eastern Nebraska and Kansas. The chief 
use of the water in this region is for irrigation. 

For the arid regions of the West this source of supply has 
been of inestimable value, and has been the means of reclaim- 
ing many an area of hitherto useless land. 

REFERENCES ON UNDERGROUND WATER 

1. Chamberlin, U. S. Geol. Surv., 5th Ann. Rept. : 125, 1885. (Artesian 
water supply.) 2. Darton, U. S. Geol. Surv., Prof. Paper 32, 1905. 
(Central Great Plains.) 3. Darton, U. S. Geol. Surv., "Water Supply 
Bulls. 57 and 161. (List of deep borings in United States.) 4. Darton, 
U. S. Geol. Surv., Bull. 138. 1S96. (Atlantic Coastal Plain.) 5. El- 
dridge, D. S. Geol. Surv., Mon. 27. (Denver basin.) 6. Fuller and 
others, U. S. Geol. Surv., Water Supply Bull. 111. 1905. (Under- 
ground waters. E. United States.) 7. Fuller, U. S. Geol. Surv., 
Water Supply Bull. 100, 1905. (Hydrography E. United States.) 
8. Gilbert, U.S. Geol. Surv., 17th Ann. Rept., II : 557, 1896. (Arkansas 



212 ECONOMIC GEOLOGY OF THE UNITED STATES 

Valley, Col.) 9. Hall, Ala. Geol. Surv., Bull. 7. (Ala.) 10. Hill, U.S. 
Geol. Surv., 21st Ann. Kept., VII : 666, 1901. (Tex.) 11. Holmes, Amer. 
Inst. Min. Engrs., Trans. XXV: 936, 1896. (Piedmont plateau.) 
12. King, U. S. Geol. Surv., 19th Ann. Kept., II : 59, 1899. (Under- 
ground water circulation.) 13. Knight, Wyo. Univ. - Exp. Sta., Bull. 
45, 1900. (Wyo.) 13 a. Lane, U. S. Geol. Surv., Water Supply Bulls. 
30 and 31, 1899 (Mich.) 14. Leverett, U. S. Geol. Surv., 17th Ann. 
Kept., II: 155, 1896. (111.) 15. Leverett, U. S. Geol. Surv., Water 
Supply Bulls. 26 and 21. (Ind.) 16. Singley, Texas Geol. Surv., 4th 
Ann. Kept. : 87. (Galveston well.) 17. McCallie, Ga. Geol. Surv., 
Bull. 7, 1899. (Ga.) 18. McGee, U. S. Geol. Surv., 14th Ann. Kept., 
II : 1. (E. United States.) 19. Norton, la. Geol. Surv., VI : 115, 
1897. (Iowa.) 20. Orton, U. S. Geol. Surv., 19th Ann. Kept., IV : 640, 
1899. (Ohio rock waters.) 21. Ruddy, Wash. Geol. Surv., 1 : 296, 
1901. (Wash.) 22. Slichter, U. S. Geol. Surv., Water Supply Paper 
No. 67, 1902. (General on underground waters.) 23. Woolman, see 
various annual reports N. J. Geol. Surv. Many other papers in 
Water Supply and Irrigation bulletins issued by U. S. Geol. Surv. 



CHAPTER XII 

SOILS 

The term soil is applied to the upper few inches of the 
mantle of unconsolidated material (regolitli) which covers 
the earth's surface, and which is composed of a mixture of 
rock, sand, and clay fragments in all stages of decay ; with 
it there is usually mixed a variable amount of decayed and 
decaying organic matter (humus). 

Origin. — Soils are classed, according to their mode of 
origin, as residual and transported. 

Residual Soils are those formed by rock weathering (see 
Residual Clay, under Clay, Chapter IV), and are found 
resting on the parent rock from whose decay they have 
originated ; they consequently, in most instances, show a 
gradual transition from the surface soil to the solid rock 
beneath. Such soils are often of great extent in the 
unglaciated areas of the South, and their clayey character 
and brilliant coloring is a marked feature. 

With this class there is sometimes grouped the humus, or 
peaty soil, formed by the accumulation of vegetable matter 
in bogs or swamps (see Peat, under Coal, Chapter I). 

Transported Soils. — The materials of residual areas are 
frequently carried away by the agency of water, ice, or wind 
and deposited elsewhere, commonly at lower levels, giving 
rise to transported soils. These are classified either accord- 
ing to their mode of origin or texture. 

213 



214 ECONOMIC GEOLOGY OF THE UNITED STATES 

The former grouping recognizes : Alluvial soils, deposited by water on 
the lowlands bordering rivers or on their deltas ; these form one of the 
most important soil types, and the fertile soils of the Nile Valley and the 
Mississippi bottoms are of this character. Their continued high fertility 
is due to the fact that the soil layer is added to annually or oftener during 
periods of flood. Glacial drift soils, representing the debris of decayed 
rocks of various kinds brought down from the north during the glacial 
period. They are made up of a mixture of many different rock types in 
all stages of decay; the continual decomposition of their component min- 
eral grains gives them a more or less permanent fertility. JEolian soils, 
or those formed by wind action, include : (1) Sand dunes heaped up by 
the action of wind along the shores of many oceans or inland seas. 
When anchored by systematic planting, they develop an abundant plant 
growth. (2) Ash soils, representing the accumulations of ash thrown 
out over a region during outbursts of volcanic activity ; these are some- 
times of high productivity, for although at first barren and sandy they 
rapidly decompose to a good soil. 

Properties of Soils. — The productivity of a soil depends 
largely on its chemical and physical properties, and to a 
lesser extent on climatic conditions. 

Chemical Properties. — The chemical analysis of a soil 
shows a variable percentage of nitrogen, silica, phosphoric 
acid, chlorine, alumina, lime, magnesia, iron oxide, potash, 
and soda, all of which, with the exception of the first, are 
derivable from mineral grains present in the soil. When 
there is a deficiency of any one of these, it is commonly 
remedied by adding fertilizers to the soil; but the value of 
the latter for plant maintenance depends not so much on the 
total quantity of each of these present, but upon the amount 
existing in soluble form. While soils vary in their composi- 
tion from place to place, there is a most marked difference 
between the soils of humid and arid regions, those of the 
latter showing a much larger proportion of fertilizing con- 



soils 215 

stituents because they have been subjected to less leaching 
action by rain water. Soils in arid regions are often covered 
by a whitish crust termed "alkali" which is composed chiefty 
of sulphates and carbonates of soda, and is formed by the 
soil water bringing these to the surface, where it escapes by 
evaporation. An excess of alkali is injurious to plants. 

Physical Properties, which are of equal importance to the 
chemical ones, include texture, structure, color, weight, and 
temperature ; a proper physical condition may often make 
up for a deficiency in plant food. The physical characters 
of a soil are produced to a large extent by natural processes, 
and can be modified but slightly by man. 

The texture of a soil refers to the size of its grains, those 
recognized being clay, silt, sand, and gravel ; depending on 
the amount of each of these present, we have clay soils, silt 
soils, loams, sandy soils, and gravelly soils. Texture is of 
importance because it affects the retentive power of the soil 
for moisture and gases. Clay soils hold much water and 
hence are wet and cold, whereas sandy soils, on account of 
the coarseness of their particles, have large pores and hold 
little water, and warm up easily. Loamy soils stand inter- 
mediate between these. 

The structure of the soil refers to the arrangement of the 
particles. If compacted, the pores are small and the soil 
holds more water, while if loose the soil behaves like sand, 
retaining little moisture. A puddled soil is one in which 
the grains are single, while in a flocculated soil the particles 
are bunched together, forming compound grains, and all good 
soils show this structure ; it increases the pore space and 
hence facilitates the circulation of air and water through the 
mass. Lime encourages flocculation. 



216 ECONOMIC GEOLOGY OF THE UNITED STATES 

The temperature of soils depends on their color and 
position with relation to the sun's rays. 

In moist climates the clay particles are washed out of the 
upper layers of the soil and settle in the lower ones, produc- 
ing a differentiation known as soil and subsoil. This is not 
found in arid regions. 

Distribution of Soils in the United States. — So varied are 
the soils of the United States that it would require many 
pages to describe,, them even partially ; nevertheless, there 
are a few well-marked types underlying extensive areas 
which may be briefly referred to. The residual soils occupy 
a large area throughout the southern states, and in the 
Appalachian belt are especially prominent, being easily recog- 
nized by their clayey character and bright colors. Glacial 
soils are prominent in the northern United States, and their 
high fertility has been noted by various writers. The alluvial 
soils are prominent in all parts of the country. In the cen- 
tral states the prairie soil is a peculiar silty type, heavily 
impregnated with humus. The loess is a silty soil, low in 
organic matter, covering many square miles of the Great 
Plains, and needs but irrigation to make it blossom with har- 
vests. Marsh soils and dune soils both cover many thousands 
of acres along the Atlantic coast ; and the latter are also ex- 
tensive around the Great Lakes as well as along the Pacific 
coast. Although reclaim able they are rarely cultivated. 

REFERENCES ON SOILS 

Hilgard, U. S. Dept. Agric, Weather Bur., Bull. 3, 1892 (Relations of 
Soil to Climate) ; King, The Soil, Wiley & Sons (New York, 1898) ; 
Merrill, Rocks, Rock Weathering, and Soils, Wiley & Sons (New 
York, 1897) ; Ramann, Forstliche Boden-kunde und Standortslehre 



soils 217 

(Berlin, 1897) ; Shaler, U. S. Geol. Surv., 12th Ann. Kept., 1 : 213, 
1891 (Origin and Nature) ; Warrington, Physical Properties of Soils 
(Oxford, Eng., 1900). See also bulletins U. S. Dept. Agric., Bur. of 
Soils, especially Nos. 4, 10, 15, 17, 18, 19, 22, and the Reports on 
Field Operations published annually. 



ROAD MATERIALS 

Under this term are included clay, sand, gravel, and differ- 
ent kinds of consolidated rock, used for covering the surface 
of a highway. In former years but little consideration was 
given to the proper selection of these materials, but now 
the subject is receiving an increasing amount of attention 
from engineers, with the results that certain required 
standards have been set up, and in many localities carefully 
adhered to. Such standards can however be applied only 
to consolidated materials. 

In many parts of the United States the roads have natural 
beds, whose character depends on that of the local formations. 
The road, therefore, may consist of clay, sand, loam, gravel, 
or bare rock, and such a road surface is unfortunately used 
even when better materials are at hand, but are overlooked 
through indifference or ignorance. 

Clay makes a hard road in dry weather, but becomes very 
sticky in wet, or even dusty after prolonged drought. Sand 
packs well if wet, but makes hard pulling when dry. Gravel, 
if ferruginous, will often cement to a good road surface, 
which wears well under light traffic. Shale will also make 
a good road. Natural road beds are, however, unsatisfactory 
at best, and artificial ones of crushed stone (macadam roads) 
are rapidly superseding them. 

For this purpose a number of different kinds of rock are 



218 ECONOMIC GEOLOGY OF THE UNITED STATES 

employed, including trap, granite, limestone, dolomite, and 
sandstone. 

The essential qualities of a stone for macadamizing are : 
(1) Hardness to resist crushing under traffic. (2) Sufficient 
abrasion to permit the formation of some dust which when 
moistened will form a cement to bind the particles together. 
(3) Freshness of the mineral grains. (4) Cheapness. Great 
variation is found to exist among the different stones with 
respect to these requirements, and even stones of the same 
kind lack uniformity. 

While the most practical test for road material is actual 
use, this is not always a cheap or rapid method, and conse- 
quently a series of physical tests has been adopted, which 
is in use in most highway laboratories. The two important 
tests are the abrasive test and impact test. In the former 
the abrasive resistance of the stone is determined, in the 
latter the cementing power of the powdered stone is meas- 
ured, by forming it into briquettes, which are broken by a 
series of blows. The same powder is remolded and again 
broken to determine its recementing power. Stones with a 
small amount of argillaceous and calcareous impurities often 
appear to have good cementing power ; but in every case the 
qualities of each stone have to be determined separately. 

Since, however, stone for road building will not bear the 
cost of long transportation, it becomes necessary to make a 
careful selection of the best that the vicinity affords. Trap 
rock and hard argillaceous limestone are perhaps more used 
than any other materials. 

Good stones for road building are more or less widely 
distributed in most parts of the United States, so that any 
detailed mention of localities is not needed. 



soils 219 



REFERENCES ON ROAD MATERIALS 

Merrill, N. Y. State Museum, Bull. 17, 1897 (N. Y.) ; Reid and Johnson, 
,Md. Geol. Surv., I and IV; Shaler, U. S. Geol. Surv., 16th Ann. 
Kept., II : 227, 1895 (Mass.). See also bulletins issued by Highway 
Division of Dept. of Agric, Wash., and Reports of Massachusetts 
Highway Commission. 



PART II 

METALLIC MINERALS 



CHAPTER XIII 
ORE DEPOSITS 

Definition. — The term ore deposits is applied to concen- 
trations of economically valuable metalliferous minerals 
found in the earth's crust, while under the term ore are 
included those portions of the ore body of which the metallic 
minerals form a sufficiently large proportion to make their 
extraction profitable. A metalliferous mineral or rock 
might therefore not be an ore at the present day, but 
become so at a later date, because improved methods of 
treatment or other conditions rendered the extraction of 
its metallic contents profitable. 

A few metallic minerals serving as ores, such as gold, 
copper, platinum, or mercury, sometimes occur in a native 
condition ; but in most cases the metal is combined with 
other elements, forming sulphides, hydrous oxides, carbon- 
ates, sulphates, silicates, chlorides, phosphates, or rarer 
compounds, the first five of these being the most numer- 
ous. A deposit may contain the ores of one or several 
metals, and there may also be several compounds of the 
same metal present. 

Gangue Minerals. — Associated with the metallic minerals 
there are usually certain common non-metallic ones which 
carry no values worth extracting. These are termed the 
gangue minerals. They often form masses in the ore deposit 

223 



224 ECONOMIC GEOLOGY OF THE UNITED STATES 

which can be avoided or thrown out in mining, but at other 
times they are so intermixed with the valuable metalliferous 
minerals that the ore is crushed and the two separated by 
special methods. 

Quartz is the most abundant gangue mineral, but calcite, 
barite, fluorite, and siderite are also common, while dolo- 
mite, hornblende, pyroxene, feldspar, rhodochrosite, etc., are 
found in some ore bodies. 

Origin of Ore Bodies. — The fact that ores form masses 
of greater or less concentration is explainable in two ways : 
either they have been formed contemporaneously with the 
inclosing rock; or else they have been formed by a process 
of concentration at a later date. The first theory is found 
to be applicable to some ores in igneous rocks, and probably 
some sedimentary ones, while the second applies to most ore 
deposits regardless of the character of the inclosing rock. 

Ores of Contemporaneous Origin. — If the ore in an igneous 
rock were formed at the same time as the rock, it would 
indicate a crystallization of metallic minerals from the 
igneous magma during cooling ; and this, in some cases, is 
true, it being found that the metallic elements in many 
basic rocks tend to segregate during cooling, sometimes 
forming masses of considerable size and of high purity. 
This mode of origin, termed magmatic segregation (18, 34, 35, 
36), was shown by Vogt to apply to the titaniferous ores of 
Scandinavia; and although the importance of the theory 
was not at first generally appreciated in America, where 
deposits of this type are rare, still it is now generally 
accepted. The best-known American examples of this 
class are the titaniferous magnetites and the chromite ores. 



ORE DEPOSITS 225 

Spurr has suggested (34) that certain ores found in acid 
rocks, such as quartz veins, have also been formed by niag- 
matic segregation. He believes that siliceous rocks, such 
as granites, may originate by differentiation from a more 
basic magma. A further development of this process 
yields quartz-feldspar rocks, and after the minerals of 
these have crystallized out, only pure silica is left, which 
forms quartz veins. Examples of this t} T pe have been 
noted by Spurr from Alaska, and by Turner from Silver 
Peak, Nevada. 

If ores in sedimentary rocks are of contemporaneous 
origin, then the deposit must be a bedded one* conforming 
to the stratification of the rock, and this explanation more- 
over requires the presence of metalliferous minerals in and 
their deposition from sea water. While certain metallic 
elements are found in the waters of the ocean, their quan- 
tity is extremely small and not to be compared with what 
may be found in disseminated or concentrated form in 
sedimentary and igneous rocks. It lias been shown, how- 
ever, that some metallic minerals, such as limonite, pyrite, 
or manganese, are occasionally precipitated on the ocean 
floor. While economic geologists have assigned a contem- 
poraneous origin to certain ores found in sedimentary strata, 
and in certain instances their theories have been quite 
generally regarded as correct (iron ores, ref. 36), still the 
majority at the present day believe that most ore deposits 
are of later date than the inclosing rock, and must have 
been formed by a process of concentration, aided in the 
majority of cases by circulating water. 

Concentration of Ores in Rocks. — In order to demonstrate 
this, it is necessary to show: (1) the presence of disseminated 



226 ECONOMIC GEOLOGY OF THE UNITED STATES 

minerals in the earth's crust ; (2) the existence of a solvent 
or carrier; and (3) the presence in most cases of cavities 
in which the precipitation of the ore can occur. 

It is well known that metallic minerals in small quanti- 
ties are widely distributed, in both igneous and sedimentary 
rocks. Sandberger (31), for example, has shown by analyses 
the presence of nickel, copper, lead, tin, and cobalt in such 
minerals as hornblende, olivine, and mica ; and Curtis has 
found traces of silver, gold, and lead in the quartz-porphy- 
ries at Eureka, Nevada (U. S. Geol. Surv., Mon. VII : 80), 
and silver, arsenic, lead, copper, gold, and silver in the 
granite at Steamboat Springs, Nevada (U. S. Geol. Surv., 
Mon. XIII : 350). Winslow has pointed out the presence 
of small quantities of lead and zinc in the limestones of 
Missouri and Wisconsin (lead and zinc, ref. 17), and 
Wagoner has made similar tests on California sediments 
(42). Since, however, the sediments were originally derived 
from the igneous rocks, it follows that the latter must be 
the original source of the minerals. It is interesting to 
note that even in the igneous rocks the metals are not 
impartially distributed, but that certain metals seem to 
favor certain rocks (De Launay, Ann. d. Min., August, 
1897, and ref. 34). Tin seems to favor granite, and chro- 
mite, peridotite. 

As regards the second point, it is now generally admitted 
that water is an important agent in the concentration of 
many ores. While cold water, free from impurities, has 
comparatively little solvent power, the presence of acids or 
alkalies materially increases its capacity for solution, and 
heat and pressure have also a great influence. Analyses of 
mine, spring, and surface waters have shown the presence 



ORE DEPOSITS 



227 



of many dissolved alkalies and other salts (24), and occa- 
sionally small quantities of metals. 

The following two analyses, which will serve as examples, 
give the calculated composition of (1) vadose, or shallow 
water, from the 500-foot level of the Geyser silver mine, 
Silver Cliff, Colorado, and (2) deep water from the 2000- 
foot level of the same mine. The ore occurs in rhyolite. 
The figures are grams per 1000 liters : — 



Si0 2 . . 
Al 2 6 3 . . 

ALA.PA 
FeC0 3 . 
MnC0 3 . 

CaC0 3 ° . 

CaF 2 " . . 
SrC0 3 . 
MgCOo . 
K 2 S0 4 " . 
KCL . . 
KBr, KI . 
Xa 2 C0 3 . 
Na 2 S0 4 . 
XaX0 3 . 
Xa 2 B 4 7 . 
LiCl . . 
C0 2 . . 
PbC0 3 . 
CuC0 3 . 
ZiiC0 3 . 



25.90 


24.42 


— 


1.06 


.SO 


— 


1.50 


7.25 


1.70 


1.19 


93.50 


366.03 


— 


Tr 


— 


Tr 


— 


3.29 


42.85 


621.84 


4.20 


19.18 


16.60 


361.34 


— 


Tr 


38.70 


1489.67 


60.50 


223.53 


— 


2.19 


— 


Tr 


— 


17.30 


37.20 


1418.61 


Tr 


1.74 


Tr 


.04 


.40 


.66 



The higher percentage of dissolved substances in the deep 
water is quite marked. 

While the importance of hot waters as an agent in the 



228 ECONOMIC GEOLOGY OF THE UNITED STATES 

formation of ore deposits is clearly recognized by many, and 
traces of metals in solution are sometimes found, still ex- 
amples of such deposits now forming are rare. Weed has 
described a hot spring near Boulder, Montana (49), which is 
depositing auriferous quartz, and the deposit is pointed out 
by him to be identical with silver and gold bearing quartz 
veins of the region between Butte and Helena, Montana. At 
Steamboat Springs, Nevada, it has been found that the allu- 
vial gravels underlying the hot spring sinters are cemented 
by stibnite and pyrite (Lindgren, Amer. Inst. Min. Eng., 
Trans. 1905 : 275). Of still more interest is the collection 
by evaporation of copper from certain Javan hot springs, 
in which the metal occurs as iodide of copper (Stevens, 
Copper Handbook, IV : 156, 1904). 

Water is known to be widely (11, 39) but not uniformly 
distributed in the rocks of the earth's crust, and much of it 
is in slow but constant circulation. While it is admitted by 
most geologists that this water has been an important ore 
carrier, collecting the disseminated metals in the rocks and 
concentrating them in localities favorable to deposition, 
still, there exists a difference of opinion regarding its 
source, one class maintaining that it is largely of meteoric 
origin, the other that it is derived chiefly from igneous 
intrusions. 

The chief exponent of the former theory is Van Hise, who 
points out that the earth's crust may be divided into three 
zones : (1) an upper zone of fracture, beginning at the sur- 
face ; (2) a zone of combined fracture and flowage ; and 
(3) a zone of rock flowage, or of no fracture. In the zone 
of no fracture the pressure is so great that any dynamic 
disturbances will cause flowage instead of fracturing, and no 



ORE DEPOSITS 229 

cavities of appreciable size can exist. The depth of this zone 
will depend on the kind of rock, Van Hise having figured 
that cavities probably cannot exist in soft shales at depths 
below 1625 feet (500 meters), and in firm granites below 
32,500 ft. (10,000 meters). 

Into this zone of no fracture, water from the surface can- 
not penetrate, but above it there may be active percolation 
by water. It is well known that rain water, falling on the 
earth's surface, seeps through the soil into the underlying 
rocks, permeating them to a variable depth, and forming a 
more or less saturated zone, whose upper limit, lying at a 
variable depth, is known as the ground- water level. In 
this zone of more or less complete saturation there is a slow 
but continual circulation, from areas of high to areas of low 
pressure, along irregular winding routes, often leading back 
to the surface and giving rise to springs. According to 
Van Hise this percolating meteoric water obtains its load of 
metallic elements from the rocks, which it- traverses in its 
passage through the zone of fracture, depositing some of it 
in the trunk channels, but being incapable of entering the 
zone of no fracture. 

The opponents (6, 18, 20, 21) of Van Hise's theory point 
to the following facts as evidence that waters of igneous 
origin are more important as ore carriers, and are the 
ones involved in deep circulation. Meteoric waters do 
not reach great depths, in fact probably not more than 
2000 feet or sometimes less from the surface, and when 
they do penetrate to a greater distance from it, it is be- 
cause they have followed some fissure. The lower levels 
of many deep mines are so dry as to be dusty. Ores have 
been concentrated at a much greater depth than that reached 



230 ECONOMIC GEOLOGY OF THE UNITED STATES 

by surface waters. It is perfectly reasonable to regard 
igneous rocks as an important source of water, and the 
experiments of Daubree have shown that a molten granite 
contains a large amount of water vapor which it retains 
while at great depths, but gives off on approaching the 
surface and cooling. While the temperature and pressure 
are still high this water escapes as vapor, and later, with 
decrease in temperature and pressure, as a liquid. Under 
favorable conditions this water may force itself upwards 
and finally mingle with meteoric waters, carrying metals 
obtained both from the liberated waters and, to a less extent, 
from the leaching of cooled igneous rock. 

It is an undeniable fact that most metalliferous veins are 
found in areas of igneous rocks, and Lindgren (see refer- 
ences on gold, 79) has shown that in the case of the gold de- 
posits of North America the periods of vein formation agreed 
closely with those of igneous activity. It is also a noteworthy 
fact that, with the exception of the deposits of commoner 
metals, such as iron, and some copper, lead, and zinc, ores 
are found in close association with igneous intrusions, which 
seems to postulate a close connection between igneous rocks 
and ore deposits, as advocated by such authorities as Weed, 
Kemp, Lindgren, and Emmons ; and although opposed by 
Van Hise, it is now held by many economic geologists that 
most metalliferous deposits, aside from ores of iron, have 
resulted hj deposition from ascending waters in regions of 
igneous intrusions, the waters being probably in large part 
at least of igneous origin. This much should be said. The 
metalliferous minerals as originally deposited have not 
always been sufficiently concentrated to serve as ores, but 
they have become concentrated at a later date by meteoric 



OBE DEPOSITS 231 

waters, as at Bisbee, Arizona. (See Ransome, under copper 
references.) Posepny (24), in his work on the Genesis of 
Ore Deposits, distinguishes between descending surface 
waters, or vadose circulations, and ascending waters from 
great depths. It is the former that have been active in 
the secondary concentration of ores. 

Formation of Cavities. — The deposition of ores in the 
rocks is greatly facilitated by the presence of cavities along 
which the ore-bearing solutions freely pass, and consequently 
a great many ore deposits occur in such spaces. There are 
a number of different ways in which cavities may be formed 
in rocks. The percolation of surface water through certain 
ones, such as limestones, often results in the formation of 
solution cavities, these in many instances attaining the size 
of veritable caverns ; a soluble rock may contain more or 
less insoluble material, such as clay or chert, which collapses 
when the surrounding rock is dissolved, and partly fills the 
cave thus formed. At times the more resistant parts are so 
bound together that they remain in their original position, 
forming a porous mass, in the cavities of which mineral 
matter is later deposited. 

Dynamic disturbances produce cavities of variable extent 
in many different rocks. These range from microscopic 
cracks, like the rift planes of granite, to enormous faults 
of great depth and linear extent, and include the joint 
planes so common in the rocks of almost all regions. Fault 
fissures form one of the most important types of passage- 
ways for ore-bearing solutions. They are often irregular, 
branching, and partly filled by fault breccia, caused by the 
breaking of the rock during the movement along the fault 
plane. A third important group of cavities in the rocks are 



232 ECONOMIC GEOLOGY OF THE UNITED STATES 

those resulting from shrinkage of the mass, which may be 
due to (1) shrinkage during cooling, as in igneous rocks ; 
(2) shrinkage during certain forms of replacement. For 
example, the change of carbonate of lime to dolomite is 
accompanied by a shrinkage of the mass, which renders the 
dolomite more porous than the original rock; and in the 
alteration of siderite to limonite there is a shrinkage of 
fully 20 per cent (25). A fourth type of channel way for the 
passage of underground water is the contact plane between 
two quite different kinds of rock, one of them fairly dense 
and impervious ; for example, the contact plane between a 
granite mass and a series of sedimentary strata. 

Precipitation of Metals from Solution. — The conditions 
which increase the solvent power of water have already been 
referred to. To this should be added the statement that 
solution generally takes place out of contact with the air. 

When, the ore-bearing solutions approach the surface or 
enter a cavity, the load of dissolved minerals is deposited 
wholly or in part, due to cooling of the solution, release of 
pressure, or by oxidation, which converts certain soluble 
salts into an insoluble form. Chemical reactions between 
two different solutions meeting in a cavity or at the inter- 
section of fissures may also cause precipitation. Iron com- 
pounds, for example, may go into solution in the form of 
carbonate, but on exposure to the air the latter is rapidly 
changed to limonite, which is insoluble. 

While the deposition of the ore often takes place in cavi- 
ties below the surface, there are cases in which it is not 
precipitated until it reaches the surface, as in a pond or in 
the soil. Certain special conditions of deposition should 
also be noted. 



ORE DEPOSITS 233 

Replacement or Metasomatism (22). — It is a well-known 
fact that under favorable conditions mineral-bearing solu- 
tions may attack the minerals of the rocks which they pene- 
trate, dissolving them wholly or in part, and depositing 
some of the original burden in place of the material re- 
moved. This replacement, termed ''metasomatism," is an 
important factor in the formation of many ore deposits, and 
may involve a total or partial loss of certain constituents of 
the rock attacked and a gain of others, even to the extent 
of introduction of entirely new compounds and elements. 
The change takes place molecule by molecule, a grain of 
vein material being deposited for each grain of replaced 
rock dissolved. The ore-bearing solutions penetrate the 
rock first along the smallest cracks, and then work their 
way into the individual mineral grains along their cleavage 
planes, until they finally permeate the entire mass. 

Metasomatic processes show great variety, and are not 
confined to one kind of rock or mineral. In its simplest 
form the result of metasomatism may often be seen in fossil- 
iferous rocks, where organic remains have been replaced by 
common mineral compounds, as in the replacement of the 
lime carbdhate of corals by quartz, or the replacement of 
molluscan shells by pyrite. From such simple conditions 
there is every gradation to the complete replacement of 
extensive areas of rock by ore, or to the extensive operation 
of metasomatism along the walls of fissure veins. In most 
cases the changes are believed to be due to the action of 
underground water ; but in some instances it seems probable 
that the processes of pneumatolysis (see below) were in- 
volved. Moreover, high temperature, pressure, and concen- 
tration seem to have been present in replacement, especially 



234 



ECONOMIC GEOLOGY OF THE UNITED STATES 



in the case of ore deposits in fissure veins. It is rarely 
possible, without examination of a thin section with the 
microscope, to decide whether minerals present are due to 
replacement or to simple interstitial filling. Fig. 37 shows 
a replacement vein in syenite. 

Some minerals are more easily replaceable than others, 
consequently the rocks in which such predominate might 

be more widely affected than 
others. (See Butte, Mon- 
tana, and Clifton, Arizona, 
under Copper.) 

The theory of metasoma- 
tism was first applied in 
America by Pumpelly in 
1871, in explanation of the 
copper deposits of Michigan; 
but the ore bodies of Lead- 
Fig. 37. -Replacement vein in Syenite v ille, Colorado, and Eureka, 

Rock, War Eagle Mine, Rossland, 

b. c. (a) granular orthociase with Nevada, were the first large 

a little sericite ; (b) secondary biotite ; . . 

(q) secondary quartz ; (c) chlorite ; deposits whose Origin was 

black, secondary pyrrhotite. After -, • i 1 •< o- xi~ 

Lindgren, Amer. Inst. Min. Eng., explained by it. Since then 

Trans. XXX: 62. fa G g re at importance of 

metasomatism has been widely recognized, and it has become 
evident that preexisting cavities are not necessary to the 
formation of ore bodies. 

Concentration by Eruptive After -action (45) QPneumatolysis}. 
— The term pneumatolysis was first used by Bunsen to 
describe the combined action of gases and water. This 
assumes that during cooling many magmas give off watery 
vapor, heated above its critical temperature (365° C.) and 
under high pressure. With this there are also mineralizing 




ORE DEPOSITS 235 

vapors and metals, combined to form volatile compounds. 
These materials, together with any other elements given off, 
may then be deposited either at the contact between the 
intrusive and the surrounding rocks, forming a true contact 
deposit, or, as in the case of the tin veins of Cornwall, Eng- 
land, in fissures formed in the surrounding rocks by the 
intrusions. Though the great importance of this class of 
ore deposits has been but recently recognized, it is now 
being found that a number of known deposits are of this 
origin. They are usually found in calcareous rocks at or 
near the contact with granitic intrusions. The ore minerals 
are specularite, magnetite, bornite, chalcopyrite, pyrite, pyr- 
rhotite, and more rarely galena and blende ; while asso- 
ciated with them are characteristic contact minerals, such 
as epidote, wollastonite, garnet, vesuvianite, and hematite. 
The sulphides sometimes carry gold and silver, but tellu- 
rides are unknown. A characteristic feature, however, 
is the association of iron oxides and sulphides, an almost 
unknown thing in fissure veins. Since these minerals are 
sometimes found in limestones of great purity, it is consid- 
ered as quite evident that in such cases, at least, most of the 
foreign matter has been derived from the igneous mass. 
Examples of contact deposits are South Mountain, Idaho, 
Seven Devils District, Idaho, and Clifton, Arizona (in part). 

Other Causes of Precipitation. — Some fifty years ago not 
a few geologists, prominent among them De la Beche, advo- 
cated the theory of ore precipitation by galvanic action (1, 9), 
and a number of experiments were made attempting to prove 
the existence of such action ; now little weight is attached 
to this theory. 

More recently Gillette (13) has expressed the view that 



236 ECONOMIC GEOLOGY OF THE UNITED STATES 

osmotic pressure is an important factor in ore deposition, 
aiding to spread the dissolved metals through the water in 
the rocks, toward centers of crystallization. 

Forms of Ore Bodies. — Ore bodies vary greatly in their 
form, and' this character has at times been used as a basis 
of classification by some writers ; but the more modern tend- 
ency is to use genetic characters instead, making form of 
secondary importance in the grouping. Certain forms of 
ore bodies are so numerous as to deserve special mention. 

Fissure Veins (8, 12, 16, 29, 47). — A fissure vein may be 
defined (22) as a tabular mineral mass occupying or closely 
associated with a fracture or set of fractures in the inclosing 
rock, and formed either by filling of the fissures as well as 
pores in the wall rock, or by replacement of the latter (meta- 
somatism). When the vein is simply the result of fissure 
filling, the ore and gangue minerals are often deposited in 
successive layers on the walls of the fissure (Rico, Colorado), 
the width of the vein depending .on the width of the fissure 
and the boundaries of the ore mass being sharp. In most 
cases, however, the ore-bearing solutions have entered the 
wall rock and either filled its pores or replaced it to some 
extent, thus giving the vein an indefinite boundary. There- 
fore the width of the fissures does not necessarily stand in 
any direct relation to the width of the vein (47) (Butte, 
Montana). 

Veins formed by the simple filling of a fissure often show 
a banded structure of varying regularity termed crustification 
by Posepny (Fig. 38), which may sometimes be brecciated 
by later movements along the fissure. Secondary bands 
may be formed after reopening of the fissures (Fig. 38), 
and such a movement may cause brecciation of the vein 



ORE DEPOSITS 



237 



material, or allow the ingress of the weathering agents 
which decompose the wall rock, giving rise to a layer of 
clay known as selvage. Where the fissure has not been com- 
pletely filled, thus leaving a central space into which the 
crystals of gangue 
project, a comb 
structure is formed. 
The bands in a 
filled fissure may 
consist of gangue 
and ore alternat- 
ing, or of different 
ores. Among the 
commonest ores 
seen in these fis- 
sure veins are py- 
rite, chalcopyrite, 
galena, blende, and 
sulphides of silver. 
Some regions af- 
ford especially fine 
examples of banded 
veins, notably those 
of Grass Valley, California, and Rico, Colorado. Abroad 
the mines of Freiberg, Saxony, and Clausthal, Prussia, also 
often yield magnificent specimens. Even in a single vein 
the ore may follow certain streaks which are termed shutes, 
or again it may be restricted to pockets of great richness, 
which are known as bonanzas. 

Fissure veins in which metasomatic action has predom- 
inated show great irregularity of width and an absence of 




Fig. 38. — Section of vein in Enterprise mine, Rico, 
Colo. The right side shows later handing due to 
reopening of the fissure. After Ransome, U. S. 
Geol. Surv., 22d Ann. Rept., II : 262. 



238 



ECONOMIC GEOLOGY OF THE UNITED STATES 



well-defined boundaries ; they also lack as a rule the sym- 
metrical banding and the breccias cemented by vein material. 
There are all gradations between these two types of fissure 
veins; and even in a single vein, simple filling may occur 
in one part and replacement in another. 

Veins often split (PL XX, Fig. 2), or intersect, and at the 
point of intersection or splitting the ore is apt to be richer. 
There are other reasons for variations in richness, among 
the most important being the character of the wall rocks, 
some kinds being more easily replaceable or more porous 
than others. Their jDhysical character will moreover exer- 
cise considerable influence on the shape and size of the 
fissure. Hard rocks like quartzite, for example, give a clean- 
cut fissure, while in soft rocks 







v^^^i?^? 



the fissure is apt to split fre- 
quently, and therefore a vein 
may be workable in one kind 
of rock, but becomes worth- 
less when passing to another, 
since the profuse branching 
interferes with economical 
mining (Fig. 39). A dike 
may also cause local irregu- 
larities, and in a given region the fissures not uncommonly 
show great variation in their direction. Thus at Butte, 
Montana, east-west veins predominate (Fig. 53), while in 
the Silverton district of Colorado they cut the rocks in all 
directions, but the majority show a north of east trend. In 
the Monte Cristo, Washington, district the veins with north- 
east trend are predominant (Fig. 40). 

Fissure veins vary considerably in their width, swelling 



Fig. 39. — Section showing change in 
character of vein passing from 
gneiss (g) to soft shale (p). After 
Beck, Lehre von der Erzlagerstat- 
ten : 13, 1901. 



ORE DEPOSITS 



239 



at some points and pinching or narrowing at others. They 
also at times show lateral enrichment ; for instance, where 
the ore cuts through stratified beds, into which the ore- 
bearing solutions have spread out laterally along the planes of 
stratification or other 
planes. It has been 
noticed in some veins, 
especially those formed 
by replacement, that 
the filling varies with 
the wall rock, at times 
changing suddenly ; 
but where the vein is 
formed wholly by the 
filling of an open fis- 
sure, the rock exerts 
no influence on the 
character of the ore 
(47). If the vein is 
inclined, the lower wall is spoken of as the foot ivall and the 
upper one as the hanging wall. 

Parallel fissures are not uncommon, but the several veins 
do not necessarily show an equal degree of richness. Where 
the vein is of composite character, — that is, consisting of 
closely spaced parallel fissures accompanied sometimes by a 
mineralization of the intervening rock, — it is termed a lode. 
The outcrop of the vein is called the apex, and is occasionally 
traceable for a long distance. 

Linked veins represent a type in which the parallel fissures 
are connected by diagonal ones (Fig. 41), giving a series 
resembling the links of a chain. 




Fig. 40. — Tabulation of strikes of principal 
veins in Monte Cristo, Wash., district. After 
Spurr, U. S. Geol. Surv., 22d Ann. Rept., 
II : 810, 1902. 



240 



ECONOMIC GEOLOGY OF THE UNITED STATES 




Fig. 41. — Linked veins. After Ordonez. 



Grash veins are a special type of fissure vein, formed by 
the enlargement of joint planes and sometimes bedding 

planes. They 
are characteris- 
tic of the up- 
per Mississippi 
Valley lead and 
zinc region, but 
are usually of 
limited extent 
and local impor- 
tance. In the 
simplest form 
they are a vertical fissure, but develop into types shown 
in Fig. 42. 

Filling of Fissure Veins (16). — The manner in which 
fissure veins have been filled, and the source of the metals 
which they contain, formed a most fruitful subject of dis- 
cussion among the earlier geologists. Four general theories 
were advanced at an early date (2). 
temporaneous formation, a 
theory no longer advocated 
b} r any one. (2) Descension, 
which likewise no longer has 
any adherents. (3) Lateral 
secretion, in which the vein 
contents are supposed to have 
been leached from the wall 
rock, usually in the immediate vicinity of the fissure, but 
at variable depths below the surface ; some geologists hold- 
ing this view believe that the area leached was very exten- 



They are: (1) Con- 




a 
Fig. 42. — Gash vein with associated 
"flats" (a) and "pitches" (&). 
Wisconsin zinc region. After Grant, 
Wis. Geol. and Nat. Hist. Surv., 
Bull. IX : 62. 



ORE DEPOSITS 241 

sive and not confined to the immediate vicinity of the 
walls. (4) Ascension, the material being deposited by infil- 
tration, sublimation with steam, sublimation as gas, or 
igneous injection. The several arguments for or against 
these theories are well set forth in Kemp's paper (ref. 16), 
and it will suffice here to state that of the various ones 
those of lateral secretion and ascension by infiltration are 
the most rational. It is probable that the majority of geol- 
ogists now believe in a modified theory of lateral secretion, 
in which the area of supply extends beyond the immediate 
walls of the fissure, and that the ore-bearing solutions have 
either ascended the fissure or entered through the walls. 




Fig. 43. — Section at Bonne Terre, Mo., showing ore disseminated through 

limestone. 

Other Forms of Ore Deposits. — Impregnations represent 
deposits in which the ore has been deposited in the pores of 
the rock, or the crevices of a breccia (Keweenaw Point, 
Michigan). Fahlband is a belt of schist impregnated with 
sulphides. Ore channels include those ore bodies formed 
along some path which the mineral solutions could easily 
follow, as the boundary between two different kinds of rock 
(Leadville, Colorado, Mercur, Utah). Bedded deposits, found 
parallel with the stratification of sedimentary rocks, and 
sometimes of contemporaneous origin (Clinton iron ore). 
Contact deposits, as now understood, represent ore bodies 
formed along the contact of a mass of igneous and sedimen- 
tary rock (usually calcareous), the ore having been derived 



242 ECONOMIC GEOLOGY OF THE UNITED STATES 

wholly or in part from the intrusive mass (Clifton, Arizona, 
in part). Chamber deposits, whose ore has been deposited in 
caves of solution (Missouri lead and zinc ores). Dissemina- 
tions, deposits in which the ore is disseminated through the 
rock (Southeastern Missouri lead ores). 

Secondary Changes in Ore Deposits. — Ore deposits may be 
changed in their upper parts by weathering agents, while the 
lower-lying portions, below the ground water level, are often 
enriched by secondary processes. 

Weathering or Superficial Alteration (25) . — This involves 
both chemical and physical changes similar to the decay and 
disintegration of common rocks, but the great number of 
mineral compounds involved, including many with metallic 
base, give rise to a large number of intricate chemical reac- 
tions. Since many of the minerals in ore deposits are more 
easily decomposed than the common rock-forming minerals, 
the alteration is quite rapid and extends to a greater depth 
than in the country rock. There is, however, marked varia- 
tion in the rate at which the different ore-forming minerals 
decay, and this variation exists even in a single group, like 
the sulphides in which the order or rate of decomposition is 
arsenopyrite, pyrite, chalcopyrite, blende, galena, chalcocite, 
and tetrahedrite (41). 

The altered portion of the ore deposit is known as the 
gossan, or iron hat (French, chapeau-de-fer ; German, eisener 
Hut), because the deposit is usually stained by iron minerals, 
such as limonite, which may sometimes completely mask the 
true nature of the ore. 

The first chemical changes are oxidation or hydration, or 
both, and these, together with other changes, produce many 



ORE DEPOSITS 243 

soluble compounds, which can be, and often are, leached out 
of the gossan by percolating waters. An example of oxida- 
tion is the alteration of pyrite to ferrous and ferric sulphate, 
and by hydration and further oxidation to limonite. Chal- 
copyrite oxidizes to copper sulphate, and by hydration and 
further oxidation to copper carbonate, silicate, or oxide. We 
see therefore that the first change in each of the above cases 
is the same, sulphates being formed from sulphides, but the 
later changes are different, the iron sulphate changing to 
hydrous oxide, while the copper forms a different set of com- 




Baxter Tun 

B.Le«l 

N...1 U«el Holbrook 

No.2 Le.el Caar and Holbrook 

No.3 L««*l Czar and Holbrook 

No. 4 L«»el Cjar and Holbrook 



Scale '■■''-,' VV /%Z&*%r- No.5 La-el Holbrook 

50 100 200 300 400 500% '-*-v * % 

i' i i i i i \ ■* % 

Fig. 44. — Section through Copper Queen Mine, Bisbee, Ariz., showing variable 
depth of weathering. After Douglas, Amer. Inst. Min. Engrs., Trans. 
XXIX., 1900. 

pounds. Reduction may, however, occur, as when, for ex- 
ample, two partly oxidized salts of iron and copper react 
with each other, giving ferric salts and metallic copper, owing 
to the stronger affinity of iron for oxygen. 

The porosity of the gossan is sometimes due to leaching, 
sometimes to shrinkage, as when siderite or pyrite change to 
limonite. Hydration, on the contrary, causes expansion. 

The depth of weathering depends on topographic condi- 
tions, chemical nature and porosity of the deposits, and 
climate ; but in any event it is liable to vary in the same 
deposit, owing to variation in the permeability of different 
parts of the mass (Fig. 44). In Arizona many copper de- 



244 ECONOMIC GEOLOGY OF THE UNITED STATES 

posits have been changed from sulphides to carbonates, to a 
depth ranging from 100 to 700 feet; the oxidized ores of 
the Appalachian region average about 100 feet in depth; 
while those of the Rocky Mountain area range from 50 to 
700 in depth. 

The ferric sulphate produced by the weathering of pyrite 
is a most important factor in the alteration of ore deposits. 
When formed it attacks pyrite and other sulphides, convert- 
ing them into sulphates, at the same time being itself reduced 
to ferrous sulphate, which is in part changed to limonite and 
sulphuric acid. That portion remaining unreduced begins 
anew the scale of change. Ferric sulphate is thus the main 
agent by which the sulphides are dissolved. Moreover it 
also acts as a solvent of free gold. 

All the metallic contents are not, however, leached from 
the gossan, for some minerals are either difficult to dissolve 
or remain unattacked. Thus in some cases the leaching 
produces an enrichment by the removal of worthless con- 
stituents and a consequent increase per ton of valuable 
minerals. The soluble compounds produced by weathering 
are often carried downward by percolating water and de- 
posited in an irregular zone between the gossau and the 
unweathered ore below. In many copper deposits there is 
found a rich zone of black copper between the gossan and 
unaltered sulphides. 

Secondary Deposition below Ground Water Level (4, 41). — 
If the body of unaltered sulphides below is broken by 
fissures, the solutions containing the various metallic sul- 
phides and sulphuric acid will enter them, penetrating at 
times to considerable depths. 

If pyrite or pyrrhotite are present at these depths, a reac- 



ORE DEPOSITS 245 

tion occurs between the ferric sulphate, the dissolved metallic 
sulphides, and the pyrite. This may result in the precipita- 
tion of new sulphides on the walls of the fracture, forming 
rich patches of ore or bonanzas (28) . The association of these 
fractures formed after the primary sulphides is an important 
character of value to the mining engineer, and from what has 
been said above, it can be seen that ore bodies lacking in iron 
pyrite will not show this secondary enrichment. It has been 
noticed, however, that pyrite is not the only reducing and pre- 
cipitating agent in ore deposits. Carbon is a strong reducer, 
and other minerals also exert a variable influence (14). (See 
deposition of lead and zinc in Wisconsin and Ozark region, 
Chap. XVII.) 

Value of Ores. — The terms rich and poor, as applied to 
ores, are used with great frequency, although most indefinite 
and often meaningless. Under very favorable conditions it 
is possible to profitably work an ore of given value at one 
locality, while if found under other less favorable conditions 
at another point it might be almost worthless. 

Those who have not given special study to ore deposits 
often fail to realize that in the majority of ores the per- 
centage of metal contained in the ore falls considerably 
below the theoretic percentage of the metallic contents in 
the ore-bearing minerals, due of course to the presence of 
a greater or less quantity of gangue minerals which tend to 
dilute the metallic values of the vein. Lake Superior copper 
ores contain as little as .65 per cent native copper ; and many 
sulphide ores running as low as 5 or 6 per cent metallic 
copper or even less are successfully worked. Many low- 
grade lead ores are profitably mined because their gold and 



246 ECONOMIC GEOLOGY OF THE UNITED STATES 

silver contents more than pay the cost of metallurgical treat- 
ment. Gold ores alone, running as low as $2 or $ 3 per ton, 
can likewise be successfully worked at times. In many cases 
the metallic contents of the ore is increased by mechanical 
concentration or by roasting (in the case of sulphides), or 
both, before the ore is smelted. 

Classification of Ore Deposits. — Many attempts have been 
made to develop a suitable classification of ore deposits, and 
many schemes have been suggested (17). These are usually 
based either on form, mineral contents, or mode of origin. 
The first is perhaps the most practical from the miner's 
standpoint, the second is undesirable because several kinds 
of ore may often be found in the same ore body, while the 
third is the most scientific, and is of value to the mining 
geologist and engineer. 

Those desiring to look into this phase of the subject in 
more detail are referred to the bibliography at the end of this 
chapter, especially the papers by Kemp (17), Posepny (24), 
and Van Hise (40). 

Only one classification is given here, viz. that of W. 
H. Weed, not because it is considered entirely satisfactory 
or especially simple, but because it embodies the results of 
the more modern studies of ore deposits and their genetic 
character. 

Classification of Ore Deposits (after Weed) 

A. Igneous, magmatic segregation. 
(a) Siliceous. 

1. Masses, Aplitic masses. Ehrenberg, Shartash. 

2. Dikes, Beresite or Aplite. Berezovsk. 

3. Quartz veins. Alaska, Randsburg, Black Hills. 



ORE DEPOSITS 247 

(b) Basic. 

1. Peripheral masses. Copper, iron, nickel. 

2. Dikes, titaniferous iron. Adirondacks, Wyoming. 

B. Igneous emanations. Deposits formed by gases above or near 

the critical point, e.g. 365° C. and 200 atmospheres for 
H 2 0. 

(a) Contact metamorphic deposits. 

1. Deposits confined to contact. Magnetite deposits, chalcopy- 

rite deposits, Kristiania type, gold ores, Bannock type. 

2. Deposits impregnating and replacing beds of contact zone. 

Chalcopyrite deposits, pyrrhotite ores, magnetite ores, Can- 
anea type, Gold tellurium ores, Elkhorn type, Arsenopyrite 
ores, Similkameen type. 

(b) Veins closely allied to magmatic veins and to Division D. 

1. Cassiterite. Cornwall. 

2. Tourmaline copper. Sonora. 

3. Tourmaline gold. Helena, Mont., Minas Geraes, etc. 

4. Augite copper, etc. Tuscany. 

C. Fumarolic deposits. 

(a) Metallic oxides, etc., in clefts in lava. Xo commercial impor- 
tance. Copper, iron, etc. 

D. Gas-aqueous or pneuniato-hydato-genetic deposits, igneous emana- 

tions, or primitive water mingled with ground water. 

(a) Filling deposits. 

1. Fissure veins. 

2. Impregnation of porous rock. 

3. Cementation deposits of breccia. 

(b) Replacement deposits. 

1. Propylitic. Comstock. 

2. Sericitic kaolinic, calcific, Copper silver, Silver lead. Clausthal. 

3. Silicic dolomitic, silver lead, aspen. 

4. Silicic calcific, cinnabar. 

5. Sideritic silver lead. Cceur d'Alene, Slocan, Wood River. 

6. Biotitic gold copper. Rossland. 

7. Fluoric gold tellurium. Cripple Creek. 

8. Zeolitic. 



248 ECONOMIC GEOLOGY OF THE UNITED STATES 

Structure Types of Above 
Fissure veins. 

Volcanic stocks, Nagyag. Cripple Creek. 
Contact chimneys. Judith. 
Dike replacements and impregnations. 
Bedding or contact planes. Leadville, Mercur. 
Axes of folds, synclinal basins, anticlinal saddles. Bendigo, 
Elkhorn. 
E- Meteoric waters. Surface derived. 

(a) Underground. 

1. Veins. 

2. Keplacements. Iron ores, Michigan ; copper ores, Michigan ; 

lead, zinc. 

3. Residual. Gossan iron ores, manganese deposits. 

(b) Surficial. 

1. Chemical. Bog iron ores, copper ores, sinters. 

2. Mechanical. Gold and tin placers. 
Sedimentary beds, iron ores, etc. 

F. Metamorphic deposits. Ores concentrated from older rocks by 
inetamorphism, dynamo or regional. 

Igneous ore deposits, forming the first division, are those 
in which the metallic minerals have crystallized directly 
from the igneous magma during cooling. 

The pneumatolytic deposits include those formed along 
igneous contacts, the material being supplied by the in- 
trusive, as explained on an earlier page. 

The gas-aqueous deposits include those which have been 
deposited from a mixture of water and steam, probably under 
pressure and at high temperature. They may either fill true 
fissures or porous deposits, or replace the wall rock lining 
a narrow fissure. It will be seen that the types mentioned 
under B and C might pass into each other. The same 
igneous mass could at great depths give off metallic min- 



ORE DEPOSITS 249 

erals under conditions mentioned under B, while higher 
up the emission from it would yield a deposit, classifiable 
under C. 

Fumarolic deposits include those in which metallic com- 
pounds are deposited from volcanic vapors or gases in clefts 
in lavas. They are of no commercial importance. 

The last class is the result of meteoric circulation, the 
waters having collected the ore particles from the rocks 
through which they moved, and deposited them under favor- 
able conditions, either on the surface or below it. 

REFERENCES ON ORE DEPOSITS 

General. 1. Barus, Amer. Inst. Min. Engrs., Trans. XIII : 417, 1885. 
(Electrical activity in ore bodies.) 2. von Cotta-Prime, Ore De- 
posits (English translation by Prime, X. Y., 1870). 3. Don, Amer. 
Inst. Min. Engrs., Trans. XXVII : 564, 1898. (Genesis of gold.) 
4. Emmons, Amer. Inst. Min. Engrs., Trans. XXX : 177,1901. (Sec- 
ondary enrichment ore deposits.) 5. Emmons, Amer. Inst. Min. 
Engrs., Trans. XXII : 53, 1894. (Geol. distribution useful metals.) 
6. Emmons, Geol. Soc. Amer., Bull. XV : 1, 1904. (Theories of ore 
deposition.) 7. Emmons, Amer. Inst. Min. Engrs., Trans. XVI : 804, 
1888. (Structural relations of ore deposits.) 8. Emmons, Colo. Sci. 
Soc, Proc. II : 189. 1885-7. (Origin of fissure veins.) 9. Fox, 
Amer. Jour. Sci. i, XXXVII : 199, 1839. (Vein formation by gal- 
vanic agency.) 10. Fuchs et De Launay, Traite des Gites Mineraux 
et Metalliferes, Paris, 1893. 11. Finch, Colo. Sci. Soc, Proc VII : 193, 
1904. (Underground waters and ore deposition.) 12. Glenn, Amer. 
Inst. Min. Engrs., Trans. XXV : 499, 1896. (Fissure walls.) 13. Gil- 
lette, Amer. Inst. Min. Engrs., Trans. XXIII, 1903. (Osmosis 
theory.) 14. Jenney, Amer. Inst. Min. Engrs., Trans. XXXII: 445, 
1902. (Chemistry of ore deposition.) 15. Kemp, S. of M. Quart., 
X : 54, 116, 326, 1889 ; XI : 359, 1890; XII : 218, 1891. (Literature 
on ore deposits.) 16. Kemp, S. of M. Quart., XIII : 20, 1892. (Fill- 
ing of veins.) 17. Kemp, S. of M. Quart., XIV : 8, 1893. (Classifi- 
cation of ore deposits.) 18. Kemp, Min. Indus., IV : 755, 1896. 
(Theories of origin of ores.) 19. Kemp, Ore Deposits of United 
States and Canada, N. Y., 1903. 20. Kemp, Amer. Inst. Min. Engrs., 
Trans. XXXIII : 699, 1903. (Relation of igneous rocks to ore 
deposition.) 21. Kemp, Amer. Inst. Min. Engrs., Trans. XXXI : 169, 



250 ECONOMIC GEOLOGY OP THE UNITED STATES 

1901. (Igneous rock and vein formation.) 22. Lindgren, Amer. 
Inst. Min. Engrs., Trans. XXX : 578, 1901. (Metasomatic processes 
in fissure veins.) 23. Lindgren, Amer. Jour. Sci. iv, V: 418, 1898. 
(Orthoclase gangue.) 24. Posepny, Amer. Inst. Min. Engrs., Trans. 
XXIII : 197, 1894. (Genesis of ore deposits.) 25. Penrose, Jour. 
Geol., II : 288, 1894. (Weathering of ore deposits.) 26. Phillips, 
Treatise on Ore Deposits, London, 1884. 27. Rickard, Eng. and 
Min. Jour., LXXIII : 106, 1902. (Recent advances in study of ore 
deposits.) 28. Rickard, Amer. Inst. Min. Engrs., Trans. XXXI : 198, 
1901. (Bonanzas in gold veins.) 29. Rickard, Amer. Inst. Min. 
Engrs., Trans. XXVI : 193, 1897. (Vein walls.) 30. Rickard, Eng. 
and Min. Jour., LXV : 494, 1898. (Minerals accompanying gold.) 

31. Sandberger, Untersuchungen iiber Erzgange, Wiesbaden, 1882. 

32. Suess, Eng. and Min. Jour., LXXVI : 52, 1903. (Hot springs.) 

33. Spurr, Eng. and Min. Jour., LXXVI : 54, 1903. (Relation of 
rock segregation to ore deposition.) 34. Spurr, Amer. Inst. Min. 
Engrs., Trans. XXXIII : 288,1903. (Magmatic segregation of rocks 
and ores.) 35. Vogt, Zeitsch. f. Prak. Geol., 1 : 4, 125, 257, 1893. 
(Magmatic segregation of ores.) 36. Vogt, Min. Indus., IV : 743, 
1896. (Formation of eruptive ore deposits.) 37. Vogt, Zeitsch. 
f. Prak. Geol., VI : 225, 314, 377, 413, 1898 ; VII : 10, 1899. (Dis- 
tribution of elements and concentration of metals in ore bodies). 
38. Vogt, Amer. Inst. Min. Engrs., Trans. XXXI : 125, 1901. (Prob- 
lems in geology of ore deposits.) 39. Van Hise, Amer. Inst. Min. 
Engrs., Trans. XXX: 27,1901. (Deposition of ores.) 40. Van Hise, 
U. S. Geol. Surv., Mon. XLVIL 1905. (Metamorphism.) 41. Weed, 
Amer. Tnst. Min. Engrs., Trans. XXX : 424, 1901. (Enrichment, gold 
and silver veins.) 42. Wagoner, Amer. Inst. Min. Engrs., Trans. 
XXX : 798, 1899. (Gold and silver in sedimentary rocks.) 43. Weed, 
Eng. and Min. Jour., LXXVI : 193, 1903. (Cross vein ore shoots.) 
44. Weed, Eng. and Min. Jour., LXXIV : 545, 1902. (Vein en- 
richment by ascending alkaline waters.) 45. Weed, Eng. and Min. 
Jour., LXXIV : 513, 1902. (Contact deposits.) Also Lindgren. 
46. Weed, Amer. Inst. Min. Engrs., Trans. XXXIII : 747, 1903. 
(Vein enrichment by ascending hot waters.) 47. Weed, Amer. 
Inst. Min. Engrs., Trans. XXXI : 634, 1901. (Influence of wall rock 
on mineral veins.) 48. Weed. U. S. Geol. Surv., Bull. 260, 1905. 
(Hot spring deposits.) 49. Weed, U. S. Geol. Surv., 22d Ann. 
Rept., II : 227, 1900. (Hot springs depositing gold.) 50. Whitney, 
Metallic wealth of U. S., Phil., 1854. 



CHAPTER XIV 
IRON ORES 

Iron is an abundant constituent of the earth's crust, and 
yet few minerals are capable of serving as ores of this metal, 
because they do not contain it in the right combination or 
in sufficient quantity to make its extraction possible or 
profitable. 

The iron ores having the greatest commercial value at the 
present day are usually those which are favorably located, 
of high quality, in considerable quantity, and possessing a 
structure such as to render their extraction easy. These 
four requirements have been met to such an eminent degree 
by the deposits located in the Lake Superior district that 
they now form the main source of supply for furnaces in 
the Eastern and Central states, many of the iron mines in 
the eastern part of the United States having been forced to 
shut down, although it is true that a number of small 
deposits are worked to supply local demand, owing to their 
proximity to furnace, flux, and coal, or because they possess 
certain desirable characteristics. 

Ores of Iron. — The ores of iron, together with their com- 
position and theoretic percentage of metallic iron, are : — 

Magnetite. Magnetic iron ore. Fe 3 4 72.4 per cent. 

Hematite. Specular iron ore, red hematite, fossil ore, 

clinton ore. Fe 2 3 70 per cent. 

251 



252 ECONOMIC GEOLOGY OF THE UNITED STATES 

Limonite. Brown hematite, bog iron ore, ocher. 

2 Fe 2 3 , 3 H 2 59.89 per cent. 

Siderite. Spathic ore, blackband, clay ironstone, 

kidney ore. FeC0 3 48.27 per cent. 

Pyrite. FeS 2 46.7 per cent. 

Of these hematite is the most valuable by far, because the 
known important deposits of it approach more closely to 
the theoretical composition than the other ores do. The 
deficiency in iron contents shown by many ores is due to 
the presence of common rock-forming minerals in the 
gangue, the impurities yielded by them being : alumina, 
lime, magnesia, silica, titanium, arsenic, copper, phosphorus, 
and sulphur. 

The effect of the last six -is to weaken the iron in general. 
While silica in high amounts is not desirable, still some fur- 
naces turn out iron for foundry purposes containing 10 or 
more per cent. Pyrite is the source of the sulphur, and 
apatite of the phosphorus. Titanium, a common but injuri- 
ous ingredient, is found in many magnetite deposits (see 
Titaniferous magnetites ; also refs. 20, 21), and up to the 
present time has rendered them practically useless, not 
because it interferes with the quality of the iron, but 
because it makes the ore highly refractory, and drives 
much of the iron into the slag. Experiments have been 
undertaken looking towards the utilization of these titan- 
iferous magnetites for the manufacture of ferro-titanium. 
Manganese, when present, is found mostly in the limonite 
ores, and for certain purposes is desirable. It is also promi- 
nent in some of the Lake Superior hematites. 

As phosphorus cannot be eliminated in either the blast furnace or the 
acid converter used in making Bessemer steel, and as the allowable limit 



IRON ORES 



253 



of phosphorus in pig iron used for this purpose is -^ percent, a distinction 
is usually made between Bessemer and non-Bessemer ores, the maximum 
amount of phosphorus permissible in iron ore to be used for this purpose 
being -^^ of the percentage of metallic iron contents of the ore. The 
phosphorus content of many high-grade ores, however, falls considerably 
below the allowable limit. 

With the exception of iron ores formed by magmatic 
segregation, gas-aqueous action, and some deposits of sedi- 




Fig. 45. — Map showing distribution of iron ores in the United States. Adapted 
from Eansome, Min. Mag., X : 1. 



mentary character, most iron ores owe their concentra- 
tion to the action of circulating meteoric waters, which 
have leached the iron out of the rocks and deposited it 
under favorable conditions either in cavities or by replace- 
ment. 

The ore most commonly formed in this manner is limonite, 
and the deposits are of surficial character, but hematite bodies 
of similar origin are known. Deposits of siderite formed 



254 ECONOMIC GEOLOGY OF THE UNITED STATES 

by replacement are frequently changed to limonite by 
weathering. Iron-ore bodies may show a variety Of form, 
but most of those known in this country are lens-shaped 
or basin-shaped in outline. 

The iron ores found in the United States are widely dis- 
tributed (Fig. 45), and their age ranges from pre-Cambrian 
to recent. The occurrence and distribution of the different 
kinds of ore are best discussed separately. 

MAGNETITE 

Magnetite occurs in the United States, (1) as lenticular 
masses commonly in metamorphic rocks; (2) as more or 
less lens-shaped bodies in igneous rocks; (3) as sands on the 
shores of lakes and seas; and (4) as contact deposits. 

The first class includes the most important deposits now 
worked in this country. The second and third groups run 
too high in titanium to have any commercial value at the 
present time, but the second may become of importance in 
the future, and moreover some of the deposits of this group 
are of large size. Undoubted representatives of the fourth 
class of commercial value are not worked. There are some, 
it is true, which occur along the contact of an intrusive and 
sedimentary rock, but their origin is ascribed to meteoric 
circulations. 

Distribution of Magnetites in the United States. — Nbn- 
Titaniferous Magnetites. — These are usually found in the 
form of lenticular deposits in metamorphic rocks. The 
most important series of occurrences is found in the crys- 
talline belt of rocks extending from New York into Alabama, 
deposits being known in New York, New Jersey, Pennsyl- 
vania, Virginia, and North Carolina. 



Plate XIV 




Fig. 1. — View of open cut in magnetite deposit, Mineville, N.Y. The pillars are 
ore left to support the gneiss hangiug wall. After Witherbee, Iron Age, Dec. 17, 
1903. 




Fig. 2. — General view of magnetic separating plants and shaft houses, Mineville, 
NY. After Witherbee, Iron Age, Dec. 17, 1903. 



IRON ORES 255 

The lenses, which are interbedded with the gneisses of 
either acid or basic character and often conform with the 
latter in dip and strike, are of variable size, and may 
occur either singly or in series, the ore body commonly 
showing pinching and swelling, or even faulting. Well- 
defined boundaries are sometimes wanting. Feldspar, 
hornblende, and quartz are common gangue minerals, 
while apatite is prominent in some. Although the ore 
as mined is frequently of sufficient purity to be shipped 
direct to the blast furnace, in some instances it is so lean as 
to require concentration by magnetic methods. This same 
plan has been adopted at Mineville, New York, to treat the 
high phosphorus magnetite, thereby yielding a rich con- 
centrate (68 per cent Fe) for iron manufacture, a fairly 
pure apatite used in making fertilizers, and a hornblende 
tailings or waste product. 

The magnetites have been extensively worked on the 
northern and eastern side of the Adirondacks, notably at 
Mineville (19), where one lens has been traced for a distance 
of 2000 feet. Many ore bodies have also been mined in 
New Jersey, where they are disposed in more or less 
parallel belts. 

The origin of these magnetites has been a subject of 
much discussion, but their interfoliation with the gneisses 
is thought by some to indicate that the ores and rock had a 
common origin. Those believing the gneisses to be meta- 
morphosed sediments thought the magnetites were originally 
limonite, but if the gneisses are metamorphosed igneous 
rocks, then the ore may represent magmatic segregations. 
The North Carolina magnetites have been suggested by 
Keith (18 a) to be replacement deposits, while Kemp be- 



256 ECONOMIC GEOLOGY OF THE UNITED STATES 

lieves that the ore bodies at Mineville (19) have been formed 
by iron-bearing magmatic waters, which were given off 
from the neighboring gabbros and penetrated the gneisses, 
while the latter were probably still at great depths and 
before their metamorphism was complete. The presence 
of apatite and fluorite shows that mineralizing vapors also 
played a part. A similar origin has recently been suggested 
by Spencer (23) to explain some of the New Jersey magnetites. 
Other theories advanced are that the magnetite deposits were 
formed as beach sands or even river bars, but such an as- 
sumption would require the gneisses to be metamorphosed 
sediments. 

A somewhat unique deposit and one of the largest ever 
worked occurs at Cornwall (17), Pennsylvania, where a bed 
of soft magnetite with some pyrite is found between Cam- 
brian limestone and Triassic shales, and against igneous 
dikes. Their age has been placed as both Cambro-Silurian 
and also Triassic, and whether they represent metamor- 
phosed pyritiferous shale or limonites is also unsettled. 
The ore runs from 40 to 55 per cent Fe and usually 
under .02 P, but is rather high in S and Si0 2 . 

Other Occurrences. — Magnetite occurs sparingly in the 
Marquette range of Michigan, where it is found in the 
schists. Other western occurrences include Colorado (6), 
Utah (32), Wyoming (la), New Mexico (la), and California. 

In the table given below there will be found the analyses 
of a number of magnetite samples from eastern mines. 

These it will be seen show considerable variation in their 
metallic iron contents, and are not all to be regarded as a 
strict average of the region which they represent. 



IRON ORES 



257 



Analyses of Magnetites 



* 


Fe 


SiO, 


P 


Mn 


A1 2 3 


CaO 


MgO 


S 


Ti0 2 


Alk 


H 2 


FeS 2 


Belvidere, N.J. . 
Little Mine, N. J. . 


51.42 

67.54 


8.85 
1.20 


1.048 
.02 


.17 

.90 


3.86 
.74 


1.68 
.31 


.18 
.51 


.08 


Tr 








McKnightstown , 
Adams Co., Pa. . 


46.90 


17.054 


P 2 5 
.128 


MnO 
.896 


4.424 


1.868 


4.198 






.953 


5.00 


.05 


Dillsburg, York Co. 
Pa 


45.00 


20.33 


P 2 6 
.107 


MnO 
.036 


3.775 


5.604 


4.129 


S0 3 
1.105 






1.14 


1.605 


Cornwall, Pa. . . 


42.70 




P 
.135 




3.411 






.62 










Mineville, N.Y. 
(Mine 21) . . . 


62.10 




P 
1.198 





















Titaniferous Magnetites. — These form a peculiar class by 
themselves, and with only one or two exceptions are found 
always associated with rocks of the gabbro family. The 
ore bodies occur in the midst of igneous intrusions, and 
according to Kemp (19, 20, 21), seem to have been formed 
by the segregation of fairly pure titaniferous iron oxide, 
either before or during the process of cooling and con- 
solidation. 

Mineralogically they may contain both ilmenite, FeO, 
Ti0 2 (FeO, 46.75; Ti0 2 , 53.25), and titaniferous magnetite, 
which is of variable composition. The gangue minerals 
may be pyroxene, brown hornblende, hypersthene, enstatite, 
olivine, spinel, garnet, and plagioclase. The ores are usu- 
ally low in phosphorus and sulphur, but Va, Cr, Ni, and 
Co are almost always present. In the United States they 
are found in New York, New Jersey, Colorado, Minnesota, 
and several other states, but are not worked. 

The following analyses illustrate their composition : — 



258 



ECONOMIC GEOLOGY OF THE UNITED STATES 



Analyses of Titaniferous Magnetites 





1 


2 


3 


4 


FeO 

Fe 2 3 

Ti0 2 

Si0 2 

A1 2 3 

Cr 2 3 

v 2 o 5 

MnO 

CaO 

MgO 

H 2 

PA 


70.50 1 

14.00 

8.60 

4.00 

1.60 
2.30 


80.78 

12.09 
2.02 
2.58 
2.40 

.03 


f 27.951 
1 15.85 J 
15.66 
17.90 
10.23 
.51 
.55 
Tr 
2.86 
6.04 
.04 
.14 


79.78 

12.08 
.75 

4.62 
.32 

Tr 
.28 
.13 

2.04 




101.00 


99.90 


99.05 


100.00 



1. Grape Creek, Colo. 

2. Mayhew Range, Minn. 



3. Split Rock, N.Y. 

4. Greensboro, N.C. 



Magnetite Sands. — These are found in those regions 
where the beach sands are composed of weathering 
products of metamorphic and igneous rocks. The sorting 
action of the waves serves to carry the heavy mineral 
grains high up on the beaches, where they form black 
streaks, composed mostly of magnetite (usually titanifer- 
ous), mixed with monazite, apatite, and other heavy min- 
erals. 

Deposits are known in this country on the shores of 
Lake Champlain, Long Island, etc., but they are of small 
extent as well as lacking in quality. 

New Zealand and Brazil are said to possess magnetite 
sands of commercial value. 



IRON ORES 



259 



HEMATITE 

This is by far the most important ore of iron in the 
United States, having in 1903 formed 86.6 per cent of 
the total production. Its distribution, however, is rather 
restricted, and about five sixths of the total quantity mined 
came from the Lake Superior region. The varieties mined 
in the United States include the earthy, specular, oolitic, 
and fossiliferous. Most of the deposits belong to the 
replacement type and are basin-shaped, while bedded and 
contact deposits are also known, but the last are not worked. 




Fig. 46. — Map of Lake Superior iron regions, shipping ports, and transportation 
lines. After Grant, Min. Mag., X: 175. 

Distribution of Hematite Ores in the United States. — At 
the present day there are but two very important hematite 
producing regions, viz. the Lake Superior region and the 
Birmingham, Alabama, area. 

Lake Superior Region. — Under this head are included a great 
series of deposits lying in the region surrounding the south 
and west sides of Lake Superior (13) . The rocks are of remote 
geological age, as can be seen from the following section : — 



260 



ECONOMIC GEOLOGY OF THE UNITED STATES 



Cambrian. 
Keweenawan. 

Upper Huronian, 

Lower Huronian. 
Archaean or 
Basement com- 
plex. 



Lake Superior sandstone. 
f Upper sedimentary, or copper series. 
\ Lower igneous, with interstratified sediments. 
C Sedimentaries w T ith local volcanics, and cut by Upper 
[ Huronian and Keweenawan intrusions. 
Sediments with some volcanics, cut by intrusives. 
Mainly ancient igneous rocks and some sediments. 
These igneous intrusions pierced by many others 
of later date. 



Each of the above series is separated from its neighbor 
by a great unconformity, due to intervals of elevation 

above the sea level and 
periods of erosion. 

The rocks of the iron- 
bearing formations are 
cherty iron carbonates; 
ferrous silicate rocks ; 
pyritic quartz rocks 
(Archaean) ; ferrugin- 
ous slates ; ferruginous 
cherts; jaspilites; am- 
phibolites and magne- 
tite schists; iron ore 
deposits; detrital fer- 
ruginous rocks from 
foregoing. Since their 
formation they have 
been folded, faulted, 
and sometimes brec- 
ciated, and it is in the 
troughs formed by folding that the ore usually occurs 
(Fig. 47). 




Fig. 47. — Sections of iron-ore deposits in Mar- 
quette range. After Van Hise. 



Plate XV 





Nk irf^r^i^Br^ 




- 


^1 -^iJV'. \ \iy& 




s3ll 


: 





Fig. 1. — Iron mine, Soudan, Minn. Shows old open pit with jasper horse in middle. 




Fig. 2. 



Outcrop of Clinton iron ore, Red Mountain, near Birmingham, Ala. 
Photo, from Tennessee Coal and Iron Company. 



IE OX ORES 



261 



The Archsean, Lower Huronian, and Upper Huronian are 
the most prod active iron-bearing formations, the last men- 
tioned containing the ore at two horizons, viz. near its base 
and in its central portion. 

Six districts, or ranges, are recognizable in the Lake 
Superior region, viz. Marquette (13) and Crystal Falls (27) 
in Michigan ; Menominee (25) in Wisconsin ; Penokee- 
Gogebic (37) on the Michigan-Wisconsin boundary; Mesabi 




Fig. 48. — Generalized vertical section through Penokee-Gogehic ore deposit 
and adjacent rocks ; Colhy mine, Bessemer, Mich. After Leitfi. 

(31) and Vermilion (28) in Minnesota. The general mode 
of occurrence of the ore in several of these is shown in 
Figs. 47, 48, and 49. 

The ore is not found at the same horizons in all the districts, the 
Marquette being the only one where all the iron-bearing formations 
of the series are found. Of these, the Archaean iron-bearing forma- 
tions are unproductive, the chief ore bodies lying within the Lower 
Huronian and at the base of the Upper Huronian. In the Crystal 
Falls district, the iron-bearing horizon of the Lower Huronian carries 
the ore as well as the horizon within the Upper Huronian. In both the 



262 



ECONOMIC GEOLOGY OF THE UNITED STATES 



Penokee and Mesabi districts the conditions are similar to those in 
the western part of the Crystal Falls district, the ore being found in a 
single formation in the Upper Huronian, while the same one in the 
Marquette region is thin and of little consequence. 

The smaller deposits are associated with plications, folding, brecci- 
ations, etc., but the larger masses of ore occur at the contact of the 
iron-bearing formations with others or between different members of 
the iron-bearing formations. These contacts were favorable for con- 
centration of ore, because they are planes or horizons of slipping, and 
the effect of this movement would be to loosen the rock, thus making- 
channels for the percolating water. Underlying the deposits of first 




Fig. 49. — Generalized vertical section through Mesabi ore deposit and adjacent 
rocks. After Leith. 

magnitude there occur impervious formations which are bent into 
troughs. Slate, quartzite, limestone, or igneous rock may all serve as 
floors, or two may combine, as in the Penokee-Gogebic district, where 
the trough is formed by the intersection of quartzite and dikes. The 
ore bodies are often U-shaped in section, being thickest at the bottom. 



The origin of these ores has for years been a puzzling 
problem to geologists (37). Foster and Whitney considered 
them eruptive, while Brooks and Pumpelly looked upon them 
as altered limonite beds. In recent years the studies of 
Irving and Van Hise (37), aided by others, have demon- 
strated that the ores owe their origin partly to a replace- 
ment of the chert. The trough-shaped location shows that 



IRON ORES 263 

the deposits were formed after the rocks had been folded, 
and it is also noticed that these troughs are even still the 
lines of underground waters. That they have been produced 
by descending waters is shown by the fact that they are on 
the upper side of the impervious bed, and because the ores 
are oxidized ones, viz., hematite and limonite. 

The chemistry of the process is thought to be as follows : Part of the 
ferric oxide was deposited as an original sediment containing silica and 
other impurities, or in some cases as sulphides or carbonates. This was 
later enriched by the addition of iron carbonate. These were originally 
contained in the rocks near the surface, and became oxidized by perco- 
lating waters, which took up the carbon dioxide liberated, and were thus 
able to dissolve iron carbonates or silicates, which they came in contact 
with in their downward course toward the troughs in which the ore is 
found. 

The precipitation of the ore was then caused by these solutions 
meeting with others which had filtered in by a more open and direct 
path from the surface, and hence contained some free oxygen, which 
converted the dissolved iron compounds into oxides. 

The same solutions, carrying carbon dioxide, dissolved the alkalies 
out of the basic igneous rocks and these waters were then able to dis- 
solve silica. In some cases the solution of silica proceeded faster than 
the deposition of the iron ore, and made the rock quite porous. The 
general result was therefore a concentration of the iron and removal 
of silica. 

The ores of the Lake Superior region vary from hard 
blue ores to soft earthy ones. They are mostly hematite, 
with small quantities of limonite, but some magnetite is 
known in the Marquette district. The following table taken 
from Birkenbine's report gives a number of typical analyses 
(1«). Many additional ones can be found in the reports on 
Mineral Resources issued annually by the United States 
Geological Survey. 



264 



ECONOMIC GEOLOGY OF THE UNITED STATES 



Typical Analyses of Lake Superior Iron Ores 



Content 


Marquette 
Range 


Menominee 
Range 


Gogebic 
Range 


Vermilion 
Range 


Mesabi 
Range 


Iron 


56.5 


55.2423 


56.308 


61.36 


56.0996 


Phosphorus . . . 
Silica 


.0353 
4.584 


.0594 
6.7693 


.0338 
3.3961 


.0373 
4.2545 


.0365 
3.4867 


Sulphur .... 
Moisture .... 


.0089 
11.85 


6.525 


10.828 


4.5649 


12.3158 



Analyses of Siliceous Ores 



Content 


Marquette 
Range 


Menominee 
Range 


Vermilion 
Range 


Iron 

Phosphorus 

Silica 


42.27 

.0316 
35.834 

.0099 
1.23 


42.129 

.0244 
34.141 

2.2 


51.1938 

.0498 

22.3642 


Sulphur 

Moisture 


3.21 



Most of the rich ores are found above the 1000-foot 
level, except in the Mesabi district where the deposits are 
shallow, as compared with their horizontal extent, some, 
however, being over 400 feet deep. 

In the early period of mining many of the Lake Superior 
bodies were worked as open cuts, but with depth underground 
working has been resorted to. There are many deposits 
in the Mesabi district which are worked as open pits from 
which the granular ore is dug with a steam shovel and 
loaded directly on to the ore cars, which are run along the 
working face (PI. XVI). 

The development of the Lake Superior region has ad- 



IRON ORES 265 

vanced with phenomenal strides. The Marquette range 
was developed as early as 1849, and the Mesabi as late 
as 1892. 

The total yield of the Lake Superior region from 1850 
to 1902 was 246,558,896 long tons. Between 1891 and 1903 
it was 191,646,959 long tons, or 77.75 per cent of the total 
amount mined. Van Hise, in estimating the available quan- 
tity of high-grade ore still in the ground, believes that 
even if it approached 1,000,000,000 long tons, mining at 
the rate of 20,000,000 tons per year would exhaust the 
supply in the first half of the twentieth century. Indeed, 
it will not be many years before lower grades of ore, 
hitherto thrown aside, will be shipped to market. Already 
ore carrying 40 per cent iron, but low in phosphorus and 
high in silica, has been sold for mixing in with high- 
grade Mesabi ores, and Van Hise believes that ores below 
40 per cent in iron will be marketed before another 
generation. 

The market value of the ores is based on the iron contents, percentage 
of water, and amount of phosphorus, and at times the manganese contents 
is taken into consideration. Some objection has been raised in the last 
few years to the fine character of the Mesabi ore and its tendency to clog 
the blast furnace, therefore requiring the admixture of lump ore from 
the other ranges ; but this objection is rapidly disappearing, and some 
furnaces now use 75 per cent of Mesabi ore in their charge. 

The Lake Superior iron ore region is not only the most important in 
the world, but the production of some of the individual mines is star- 
tling. This enormous output can, perhaps, be best appreciated by some 
comparative figures. Thus, for example, the production of 15,371,396 
long tons of ore mined in Minnesota in 1903 is about three quarters of 
the total amount extracted from the famous magnetite deposits of 
Cornwall, Pennsylvania, since they were opened in 1740, or of the total 



266 



ECONOMIC GEOLOGY OF THE UNITED STATES 



quantity of New Jersey magnetites mined since they were first worked in 
1710. The production even of single mines is often great, six mines in 
1903 producing over 1,000,000 long tons of ore each (1 a). 

Clinton Ore (35, 36, 30). — This ore, which is also called 
fossil, pea, or dyestone ore, was given the first name on 
account of the ore bed having been originally discovered at 
Clinton, New York. It is one of the most persistent iron- 
ore deposits that is known, for it occurs wherever rocks 
belonging to the Clinton stage of the Silurian are found, 




Fig. 50. — Section Clinton ore beds, Oxmoor, Ala. a, red sandstone, 5' ; 
b, yellow sandstone, (5'; c, red sandstone, 15'; d, ore, 22', upper 2' soft; 
e, shale, 6' : /, rich ore, 2' 6". After Smyth, Amer. Jour. Sci., June, 1892. 

including many localities, therefore, along the line of the 
Appalachians from New York to Alabama, as well as in 
Ohio and Wisconsin. In Pennsylvania there are several 
belts of the ore, owing to the presence of many eroded folds 
carrying the Clinton rocks. 

The ore is interstratified with sandstones and shales, varies 
in thickness from a few inches to ten or twenty feet, is at 
times oolitic in its structure, and at others is made up of a 
mass of small fossils. At Birmingham, where the greatest 
development has occurred, the ore occurs in a ridge known 
as Red Mountain, the bed having a shale roof and sandstone 



IRON ORES 267 

floor, while the thickness of the main bed varies from twelve 
to twenty feet. The beds dip gently to the east, and the 
iron ore is worked by means of slopes, although the early 
workings at some of the mines were open cuts, on account 
of the thin overburden. The prominence of this locality is 
due to peculiar conditions, the ore being bordered on the 
west by Cambrian limestone which forms the valley floor, 
while on the western side of the valley the coals of the 
Warrior Field outcrop. Thus the three essential elements 
for iron manufacture are brought in close contact by folding 
and faulting. East of the iron range are two additional 
coal basins. 

The great development of this ore in Alabama is due 
partly to favorable local conditions and partly to its re- 
moteness from the Lake Superior region. 

The origin of these ore bodies has been argued from 
different standpoints, some holding that they represent 
altered limestone beds (35 a), because of the presence of 
fossils in them, while the concentric nature of the oolites, 
with a nucleus of worn quartz grains, has led others, espe- 
cially Smyth, to ascribe a concretionary origin (36) to them. 
The former theory is strengthened by finding at many 
places an increase of the lime contents of the ore with the 
depth. Thus at Attalla, Alabama, the Clinton limestone at 
250 feet from the surface carries only 7.75 per cent of iron, 
while at the outcrop it has 57 per cent of iron. 

The Clinton iron ores usually run high in phosphorus and also silica. 
Of the two following analyses, Xo. 1 is hard ore and No. 2 soft ore. The 
latter runs higher in lime. A difference also appears to exist between 
the composition of the fossil or upper ore bed and the oolitic or lower 
ore bed, as represented by analyses 3 and 4 (30) of the following table: — 



268 



ECONOMIC GEOLOGY OF THE UNITED STATES 





1 


2 


3 


4 


Fe . 

Fe o Q 


52.87 

.43 

.11 

13.66 

6.13 

1.26 

.37 

.30 

1.62 

.08 


37.00 

.37 

.07 

13.44 

3.18 

16.20 

.50 
12.24 


30.24 
.75 

.15 

8.71 

3.67 

20.64 

7.84 

24.78 


46.04 


P 




P 


1.29 


s 




so 3 

Si0 2 

A1 2 0^ 


.20 

16.82 

3.54 


CaO 


9.96 


MffO 


3.41 


MnO 




H 2 




C0 9 


13.62 



Other Occurrences. — Extensive deposits of hematite in 
Carboniferous limestone are found in Laramie County, Wyo- 
ming (1). The ore carries 60 to 67 per cent iron, 1\ to 5 per 
cent silica, and is low in phosphorus. In New Mexico, near 
Hanover, a deposit carrying about one quarter hematite and 
three quarters magnetite, along the contact of granite and 
limestone, is also extensively worked. Deposits of hematite 
in brecciated Carboniferous limestones, and formed proba- 
bly by replacement, are known in Iron and Washington 
counties of southwestern Utah, and are probably the largest 
iron-ore deposits in the West. Other deposits are found 
in the Wasatch Mountains, along the contact of andes- 
ite and limestone. The ore here consists of hard black 
crystallized hematite and magnetite, associated with chal- 
cedony and crystalline quartz. Leith (32) considers it to be 
a replacement deposit. While much of the ore is of good 
quality, it is mostly non-Bessemer. The Utah deposits are 



IRON ORES 269 

at present too far from the railroad to be of much value, 
but are to be looked on as an important future source of 
supply. Specular hematites also occur at Pilot Knob, Mis- 
souri, interstratified with breccias and porphyry sheets, and 
were formerly much worked. 

LIMONITE 

Limonite (41-52) or brown hematite is, like magnetite, of 
comparatively little importance in the United States as 
compared with hematite, having yielded an average of but 
12.2 per cent of the total iron production of the United 
States in the last fifteen years, and but 8.8 per cent of the 
total domestic iron ore production in 1903. 

Although deposits of limonite are widely scattered over 
the United States, about nine tenths of the total quantity 
comes from the deposits located in western New England 
and the Appalachian belt. 

Owing to their mode of origin, limonites are rarely of 
high purity, being commonly associated with more or less 
ferruginous clay, which has to be separated from the ore by 
washing. 

Limonite may occur under a variety of conditions and 
associated with different kinds of rocks, but two impor- 
tant types are recognized, viz. bog ores, and residual 
limonites. 

Bog Ores. — The bog ores are formed by the precipitation of 
limonite in swamps, ponds, or lakes. The iron is dissolved 
from the rocks or soil by percolating waters charged with 
carbon dioxide or organic acids, either in the form of ferrous 
carbonate or ferrous sulphate. As these iron-bearing waters 



270 



ECONOMIC GEOLOGY OF THE UNITED STATES 



discharge into the ponds the iron compounds are oxidized 
to hydrous ferric oxide or limonite, which settles on the 
bottom. Such ores are usually impure from an admixture of 
sand or clay which has been deposited at the same time, and 
are rarely of any thickness. They are of no commercial 
value in the United States, but in foreign countries are 
worked in Sweden, in which kingdom they have been known 
to accumulate in ponds to the depth of 18 inches or more 
every 15 to 30 years. The ore is collected periodically 
by dredging. 

Residual limonites. — The residual limonites are a much 
more important class, and form (1) by the weathering of 




Fig. 51. — Section illustrating formation of residual limonite in limestone. After 
Hopkins, Geol. Soc. Amer., Bull. XI : 485. 

pyritiferous veins (see gossan, Chapter XIII), or (2) more 
often from the weathering of ferruginous rocks. The sec- 
ond process results in the formation of deposits of iron- 
stained clay scattered through which are nodules and 
irregularly shaped masses of limonite, these making up 
from 5-10 per cent of the entire mass. 

The limonite may accumulate first by deposition in the 
cracks of the rock, or by impregnation or replacement, and 
prior to the breaking down of the rock to a mass of residual 
clay. Since these deposits often represent the concentra- 
tion of iron from a great thickness of rock, it is not 



Plate XVII 




Fig. 1. — Pit of residual limonite, Shelby, Ala. After McCultey, Ala. Geol. Surv. 
Report on Valley Regions, Pt. II: 77, 1897. 




Fig. 2. — Old limonite pit, Ivanhoe, Va., showing pinnacled surface of limestone 
which underlies the ore-bearing clay. The level of surface before mining 
began is seen on either side of excavation. H. Ries, photo. 



IRON ORES 271 

necessary that the parent material contain a high percentage 
of iron. 

An important belt of residual limonites of Cambro-Silurian 
age, and associated with slates, schists, or limestone, is found 
extending from Vermont to Alabama, along the Great Valley, 
and consisting of beds of residual clay carrying limonite 
nodules (42, 44-48 a). This type of deposits is worked from 
Vermont to Alabama, and some of the larger mines in the 
latter state have an annual production of over 100,000 tons. 
Those found in Georgia are associated with manganese. 
Plate XVII, Fig. 2, shows the irregular surface of the 
Cambro-Silurian limestone in one of the Virginia pits. 

In addition to these, important deposits are found in Vir- 
ginia, representing the weathered portion of a great belt of 
pyrite bodies. This extends for over 20 miles and is known 
as the " Great Gossan Lead," its contents averaging from 
40 to 41 per cent metallic iron (48 6, see also Copper, Duck- 
town, Tennessee). 

The Oriskany formation also carries large deposits of 
limonite to the westward of the Cambro-Silurian belt, and 
these are actively worked in Virginia (49). 

Other Occurrences. — Limonites of more or less distinctly 
bedded character are found in the Tertiary of northeastern 
Texas (50, 52), where they occur as thin beds capping the hills 
and are mined for local use (50). Others are found at the same 
horizon in Arkansas but promise to be of little commercial 
value. In the former case they are closely associated with 
greensands, and may have formed by weathering either from 
these or from pyrite grains. Small deposits are known in 
Iowa (41), Wisconsin, Minnesota, and Oregon (3a). Much 
limonite, at times manganiferous and containing even small 



272 



ECONOMIC GEOLOGY OF THE UNITED STATES 



quantities of silver, is obtained from the gossan of the Lead- 
ville ore bodies. Its chief use is as a flux. 

The following analyses give the composition of limonites 
from several localities. 

Analyses of Limonites 



Average composition Alabama 
limonite 

Average of 29 commercial 
analyses, Pa., Cambro-Silurian 
ores 

Eusk, Cherokee Co., Texas . . 

Allamakee County, la. ... 



Fe 


P 


S 


Si0 2 


AI2O3 


CaO 


MgO 


H2O 


Moist. 


48.54 


.38 
P 2 5 


.09 


11.22 


3.61 


.84 




6.00 


7.00 


43.47 


1.10 


.06 
S0 3 


18.97 


2.39 


.48 


.42 




11.62 


44.68 


.09 


.20 


18.90 


5.76 


.18 


Tr 


11.03 




54.32 


1.8 


— 















Mn0 2 



.85 



Those of the Appalachian belt are much used by pig-iron 
manufacturers because, owing to their siliceous character, 
they can be mixed in with high-grade Lake Superior ores 
which are deficient in silica. They are also cheaper, and 
their mixture with other ores seems to facilitate the reduc- 
tion of the iron in the furnace. 



SIDERITE 

Siderite (53-58) is the least important of all the ores of 
iron mined in the United States, both on account of the 
small quantity and its low iron contents. When of con- 
cretionary structure, with clayey impurities, it is termed 
clay ironstone, and these concretions are common in many 
shales and clays. In some districts siderite forms beds, 
often several feet in thickness, but containing much bitumi- 
nous and argillaceous matter, and known as blackband ore. 
This is found in many Carboniferous shales. 



IRON ORES 273 

Eastern Ohio (54) and Kentucky (53) and western Penn- 
sylvania (55) are the most important producing states. The 
ore is obtained chiefly from the Lower Coal measures, 
although known in the other stages of the Pennsylvania 
series. Another important occurrence is at the Burden 
Mines, near Hudson, New York (56), where lens-shaped 
beds of clay ironstone are found in the Hudson River 
shales and sandstones. The beds have been folded and 
faulted, so that the ore bodies lie in basins. The ores 
are rather magnesian, and on this account it has been 
suggested by Kimball that they have been formed in shore 
waters receiving drainage from the Archaean Highlands ; 
they are also high in phosphorus. Siderite is of far greater 
importance in foreign countries, and large quantities are 
shipped to the United States from Spain. It is roasted 
for use, thereby expelling the carbonic acid and raising 
the iron contents. 

Production of Iron Ores. — The iron ore mining industry 
in the United States has progressed with phenomenal 
strides, and this country now leads the world in the pro- 
duction of iron ore. Indeed, so great has the production 
become that in 1903 it was equal to the combined output 
of Germany and Luxemburg and the British Empire for 
1902. Moreover, the average iron content of the ore 
mined in the United States is higher than that mined 
in foreign countries, thereby resulting in the production 
of a greater amount of pig iron from a given quantity of 
ore. 

The Lake Superior region is now producing at least three 
quarters of the iron ore used in the United States, and it 



274 



ECONOMIC GEOLOGY OF THE UNITED STATES 



has much the largest reserves of high-grade ores, but even 
these may be exhausted in fifty years or less at the present 
rate of consumption. The low-grade ores of this region 
and others will, however, be available for a much longer 
time. 

While there is not danger of the present supply of 
ore soon becoming exhausted, still with the present con- 
sumption it is well to consider possible sources of the 
future. 

In the United States the Utah and some other western 
deposits will no doubt be drawn upon, and many ores now 
looked upon as too low grade to work will also be con- 
sidered. Aside from domestic sources of supply there are 
foreign ones which may perhaps be eventually turned to, 
such as those from Canada, Newfoundland, and Brazil on 
this side of the Atlantic, or even those of Scandinavia on the 
European side. In the last-mentioned country especially 
attention has been drawn in the last few years to mag- 
netite deposits located well within the Polar circle and of 
stupendous size. 

The production of iron ores in the United States from 
1889 to 1903 was as follows : — 

Total Production of Iron Ores in the United States 



Year 


Long Tons 


Year 


Long Tons 


1889 


14,518,041 


1895 


15,957,614 


1890 


16,036,043 


1896 


16,005,449 


1891 


14,591,178 


1897 


17,518,046 


1892 


16,296,666 


1898 


19,433,716 


1893 


11,587,629 


1899 


24,683,173 


1894 


11,879,679 


1900 


27,553,161 



IK OX ORES 



275 



Production of Iron Ore in the more Important States from 

1901 to 1903 



1901 

Long Tons 



1902 

Long Tons 



1903 

Long Tons 



Minnesota 

Michigan 

Alabama 

Tennessee 

Virginia and West Virginia 

Wisconsin 

Pennsylvania 

New York 

New Jersey 

Georgia 

Other states 

Total 



11,109,537 

9,65-1,067. 

2,801,732 

789,191 

925,391 

738,868 

1,010,684 

420,218 

401,989 

215,5991 

789,897 



15,137,650 
11,135,215 
3.574.474 
874.542 
987,958 
783.91)6 
822.932 
555.321 
441,879 
364,890 2 
875,278 



15.371,396 
10,600,330 
3,684.960 
852,704 
801,161 
675,053 
644.599 
540,460 
484,796 
443.452 
920.397 



28.887,479 



35.554.135 



35.019.308 



Production of Lake Superior Iron Ores by Ranges 





1901 


1902 


1903 


Range 


Long Tons 


Long Tons 


Long Tons 


Gogebic 


3,041,869 


3,683.792 « 


3,422,341 


Marquette 


3,597,089 


3,734,712 


3,686.214 


Menominee 


3,697,408 


4,421,250 8 


4,093,320 


Mesabi 


9,303,541 


13,080,118 


13.152.812 3 


Vermilion 


1,805,996 


2,057,532 8 


1,918,584 



Production of Most Important Iron-Ore Producing Countries 



Country 



Year 



Quantity 
Long Tons 



Percentage 
World's 

Production 



United States 

Germany and Luxemburg 

Great Britain 

Spain 

Russia and Finland. . . 

France 

Sweden 

Austria-Hungary . . . 



1903 
1903 
1903 
1903 
1902 
1902 
1903 
1902 



35,019,308 

21.230,639 
13.715.645 
8,478,600 
5,648,227 
5,003,782 
3.677.841 
3.329,128 



34.71 
21.04 
13.59 
8.40 
5.60 
4.96 
3.65 
3.30 



1 Includes North and South Carolina. 

3 Maxima. 



2 Includes North Carolina. 



276 ECONOMIC GEOLOGY OF THE UNITED STATES 

The exports of iron ore from the United States in 1903 
amounted to 80,611 long tons, valued at $255,728. 

REFERENCES ON IRON ORES 

General. 1. Birkenbine, Chapters on Iron Ores in Mineral Resources of 
United States, published annually by U. S. Geol. Survey ; 1 a. Mining 
Census, 1902, Mines and Quarries. 2. Kimball, Anaer. Geol., XXI : 
155, 1898. (Concentration by weathering.) 3. Penrose, Jour. 
Geol., 1 : 356, 1893. (Chemical relations of iron and manganese.) 
3 a. Putnam, Tenth Census, XV. 4. Swank, Eng. and Min. Jour., 
LXXIII: 347, 1902. (U. S. iron and steel works.) 5. Winchell, 
Amer. Geol., X : 277, 1892. (Theories of origin.) 

State Reports. 6. Chauvenet, Amer. Inst. Min. Engrs., Trans. XVIII : 
266, 1890. (Colo.) 7. Nason, Mo. Geol. Surv., II, 1892. (Mo.) 
8. Nitze, N. Ca. Geol. Surv., Bull. I, 1893. (N. Ca.) 9. Orton, 
Ohio Geol. Surv., V: 371, 1884. (Ohio.) 10. Putnam, 10th Census, 
XV: 467. (U.S.) 11. Shaler, Ky. Geol. Surv., New Series, III : 163, 
1877. 12. Smock, N. Y. State Museum, Bull. 7, 1889. (N.Y.) 
13. Van Hise, U. S. Geol. Surv., 21st Ann. Rept., Ill : 305, 1901. 
(Lake Superior region.) 14. Winchell, Minn. Geol. Surv., Bull. 6, 
1891. (Minn.). 

Special- Papers. Magnetite. 15. DTnvilliers, Second Pa. Geol. Surv., 
D3, II, pt. 1 : 227, 1883. (Berks Co.) 16. Prime, Ibid. 1 : 190, 
1883. (Lehigh Co.) 17. DTnvilliers, Amer. Inst. Min. Engrs., 
Trans. XIV: 873, 1886. (Cornwall.) 18. Hulst, Eng. and Min. 
Jour., LXXVIII : 350,1904. (Titaniferous ores.) 18 a. Keith, U.S. 
Geol. Surv., Bull. 213 : 243, 1903. (N. Ca.) 19. Kemp, Amer. 
Inst. Min. Engrs., Trans. XXVII: 146, 1898. (Mineville, N.Y.) 
20. Kemp, U.S. Geol. Surv., 19th Ann. Rept., Ill: 377, 1899. 
(Adirondack titaniferous ores.) 21. Kemp, S. of M. Quart., XX: 
323, 1899. (Titaniferous magnetites.) 22. Nason, Amer. Inst. Min. 
Engrs., Trans. XXIV: 505, 1895. (N.J.) 23. Spencer, Min. Mag., 
X: 377, 1904. (N.J.) 24. Wolff, N. J. Geol. Surv., Ann. Rept. for 
1893: 359, 1894. (N.J.) 

Hematite. 25. Bayley, U. S. Geol. Surv., Mon. XLVI, 1904. (Menomi- 
nee range.) 26. Boutwell, U. S. Geol. Surv., Bull. 225: 221, 1904. 
(Uinta Mts., Utah.) 27. Clements, Smythe, Bayley, and Van Hise, 
U. S. Geol. Surv., 19th Ann. Rept., Ill : 1, 1899. (Crystal Falls 
district.) 28. Clements, U. S. Geol. Surv., Mon. XLV, 1903. (Ver- 
milion range.) 29. Dewees, Second Pa. Geol. Surv., Rept. F, 1878. 
(Pa.) 30. Eckel, Eng. and Min. Jour., LXXIX : 897, 1905. 31. Leith, 



IRON ORES 277 

U. S. Geol. Surv., Mon. XLIII, 1903. (Mesabi range.) 32. Leith, 
U. S. Geol. Surv., Bull. 225: 229, 1904. (S. Utah.) 33. McCreath, 
Second Pa. Geol. Surv., MM : 229, 1879. (Many analyses.) 34. Pechin, 
.Amer. Inst. Min. Engrs., Trans. XIX : 1016, 1891. (Va.) 35. Porter, 
Amer. Inst. Min. Engrs., Trans. XV: 170, 1887. (Term., Ala., Ga.) 
35a. Russell, U.S. Geol. Surv., Bull. 57: 22, 1889. (Clinton ore.) 
36. Smyth, Amer. Jour. ScL, XLIII : 487, 1892 (Clinton ore) ; and 
N. Y. State Geologist, 22d Ann. Rept., 1902 : 116, 1904. 37. Van Hise, 
U. S. Geol. Surv., 21st Ann. Rept., Ill: 305, 1901. (Lake Superior 
region.) 37 a. Van Hise, Bay ley and Smyth, U. S. Geol. Surv., Mon. 
XXVIII, 1897. (Marquette.) 38. Van Hise and Irving, U. S. Geol. 
Surv., Mon. XIX, 1892. (Penokee-Gogebic range.) 39. Weidman, 
Wis. Geol. and Nat. Hist. Surv., Bull. 13, 1904. (Baraboo district, 
Wis.) 40. Woodbridge, Series of articles on Mesabi range, Eng. and 
Min. Jour., 1905. 

Limonite. 41. Calvin, la. Geol. Surv., IV: 101, 1895. (la.) 42. Cat- 
lett, Amer. Inst. Min. Engrs., Trans. XXIX : 308, 1900. (Va.) 
43. Diller, U. S. Geol. Surv., Bull. 213 : 219, 1903. (Redding quad- 
rangle, Calif.) 44. Eckel, Eng. and Min. Jour., LXXVIIT : t32, 
1904. (E. N. Y. and W. New Eng.) 45. Garrison, Eng. and Min. 
Jour., LXXIII : 258, 1904. (Chemical characteristics.) 46. Hayes, 
Amer. Inst. Min. Engrs., Trans. XXX : 403, 1901. (Ga.) 47. Hayes 
and Eckel, U. S. Geol. Surv., Bull. 213 : 233, 1903. (Cartersville, Ga.) 
48. Hopkins, Geol. Soc. Amer., Bull. XI : 475, 1900. (Pa.) 48 a. Mc- 
Calley, Ala. Geol. Surv., Report on Valley Region, II, 1897. (Ala.) 
48 b. Moxham, Amer. Inst. Min. Eng., Trans. XXI: 133. (Great 
Gossan Lead.) 49. Pechin, Eng. and Min. Jour., LIV : 150, 1892. 
(Va. Oriskany ores.) 50. Penrose, Geol. Soc. Amer., Bull. Ill : 44, 
1892 (Ark. and Tex. Tertiary ores) ; also Ark. Geol. Surv., Rep. 
1892, vol. 1, 1892. 51. Phillips, Eng. and Min. Jour., LXV : 489, 
1898. (Ala.) 52. Walker, Tex. Geol. Surv., 2d Ann. Rept., 291, 
1891. (Cherokee Co., Texas.) 

Siderite. 53. Moore, Ky. Geol. Surv., 2d Ser., I, pt. 3 : 63, 1875. (Ky.) 
54. Orton, Ohio Geol. Surv., V : 378, 1884. (Ohio.) 55. Second Pa. 
Geol. Surv., K: 386, and MM: 159, 1879. (Pa.) 56. Raymond, 
Amer. Inst. Min. Engrs., Trans. IV : 339, 1875. (N.Y.) 57. Smock, 
N. Y. State Museum, Bull. 7 : 62, 1889. (N.Y.) 



CHAPTER XV 



COPPER 



Ores of Copper. — Copper-bearing minerals are not only 
numerous, but widely although irregularly distributed. 
More than this, copper is found associated with nearly 
every variety of ore or ore deposit. Nevertheless but few 
minerals serve as ores of copper, and the same may be said 
regarding the number of important producing districts in the 
United States. 

The ores of copper together with their theoretic composi- 
tion are as follows : — 



Ore 

Native copper 

Chalcocite 

Chalcopyrite 

(Copper pyrite) 
Bornite 

(Horseflesh ore) 

Tetrahedrite 

Enargite 

Melaconite (Black oxide) 

Cuprite 

Azurite 

(Blue carbonate) 
Malachite 

(Green carbonate) 
Chrysocolla 



Composition 



Cu 


S 


100 




79.8 


20.2 


34.5 


35.0 


55.5 


28.1 


52.1 


23.10 


48.40 


32.50 


79.86 




88.80 




55.00 




57.40 




36.10 





Fe 



Cu 

2u 2 £ 
CuFeS, 



Cu 2 S 



Cu 3 FeS 3 



4 Cu 2 S, Sb 2 S 8 

Cu 3 AsS 4 

CuO 

Cu 2 

3 CuO, 2C0 2 +H 2 

2 CuO, CO,, H 9 



CuO, Si0 2 , 2 H 2 



30.5 
16.4 
1.39 



278 



copper 279 

Very few ores approach the theoretic percentages given 
above. Thus in Michigan, where native copper is the ore 
mineral, this, as now mined, rarely averages above 1 per 
cent metallic copper. At Butte, Montana, the copper-bear- 
ing minerals are chalcocite, enargite, bornite, and chalco- 
pyrite, but much of the ore does not usually contain more 
than 5 or 6 per cent metallic copper, and in rarer instances 
12 per cent. The same holds true in many other regions. 
At the present time chalcopyrite is probably the most widely 
distributed of all the copper ores, and the one most often 
worked, but it is not the prominent ore in the largest pro- 
ducing districts. 

Copper ores are found in many formations, ranging from 
the pre-Cambrian to the Tertiary, but grouped according to 
their mode of origin they fall mostly into one of the four 
following groups (2) : — 

1. Magmatic segregations. No workable deposits of this 
type are known in the United States. 

2. Contact metamorphic deposits, in crystalline, usually 
garnetiferous limestone, along igneous rock contacts. The 
copper is thought to have been introduced by vapors from 
the igneous rock. 

3. Deposits formed by ascending, circulating, probably 
hot waters, the ores being deposited in fissures, pores, spaces 
of brecciation, or sometimes by replacement of the rock. 

4. Pod or lens-shaped deposits in crystalline schists, which 
may represent concentration of material from a disseminated 
condition in the surrounding rocks. 

While the third and fourth groups include all the largest 
deposits of the world, still these do not in all cases owe their 
economic importance to the mode of formation, but rather to 



280 ECONOMIC GEOLOGY OP THE UNITED STATES 

secondary changes which have taken place in them, resulting 
in a leaching of the copper in the upper part of mass, as 
copper sulphate, and its transference to lower levels, where 
it is redeposited through the influence of copper sulphide, 
iron compounds, or limestone. 

Impurities in Copper Ores. — The impurities which copper 
ores may contain are iron, silver, antimony, arsenic, tellurium, 
silica, sulphur, and phosphorus, and in the metallurgical treat- 
ment of the ore it is desirable to rid the metal of these as 
fully as possible. Both iron and silver may affect the elec- 
trical conductivity of copper, and antimony and arsenic do 
so to a smaller extent. 

Tellurium is not uncommon in some districts, and renders 
the metal red-short even in small amounts. Silver, even 
if present in as small amounts as .5 per cent, lowers the 
electrical conductivity, and above 3 per cent affects the 
toughness and malleability of the copper. Sulphur up to 
.25 per cent lowers the malleability and .5 per cent renders 
the metal cold-short, while .4 or more per cent phosphorus 
makes it red-short. 

Many low-grade ores can be concentrated by crushing and 
mechanical concentration, as in the Lake Superior district of 
Michigan and at Butte, Montana. Sulphide ores may also 
be given a preliminary roasting to get rid of the volatile 
sulphur, arsenic, etc. The ore is then usually put through 
a smelting process, followed sometimes by electrolytic treat- 
ment for refining the metal. 

Superficial Alteration of Copper Ores (see 25, ore deposits). 
— This may produce results of great economic importance, 
and excellent examples of it are seen in some of the Arizona 



COPPER 281 

deposits, where the upper portions of the copper deposits are 
brown or black ferruginous porous masses brightly colored 
with oxidized copper minerals such as cuprite, malachite, 
azurite, and chrysocolla, while below this at a variable depth 
they pass into sulphides. 

In weathering, the copper minerals, such as chalcopyrite 
or other sulphides, are usually oxidized first to sulphates, 
and subsequently changed to oxides, carbonates, or silicates 
and occasionally even to chlorides and bromides. A con- 
centration of the ore deposit may take place partly by segre- 
gation and partly by leaching, and pockets of the ore form, 
which are surrounded by oxidized iron minerals forming 
part of the gangue. 

While the oxidation will not increase the total copper 
contents of the ore body, still it may change it into a more 
concentrated form, for the carbonates and other oxidized 
copper minerals contain more copper than the original sul- 
phide. The ore in the gossan may therefore run from 8 to 30 
per cent or more, while below it may show only 5 per cent of 
copper (see 25, ore deposits). These altered ores can gener- 
ally be more cheaply treated. If leaching follows oxidation, 
the gossan may be freed of its ore, as at Butte, Montana, 
where the upper part of the ore-bearing fissures is poor 
siliceous gangue. Secondary enrichment may also occur 
below the water level, giving chalcocite, chalcopyrite, and 
bornite of later origin. 

Distribution of Copper Ores in the United States. — About 
90 per cent of the copper produced in the United States is 
obtained from three states, viz. Montana, Michigan, and 
Arizona, named in the order of their output, the rest coming 



282 



ECONOMIC GEOLOGY OF THE UNITED STATES 



from the Appalachians and Cordilleran area ; the ores of the 
latter are often worked chiefly for their gold contents, with 
copper as a secondary product. 

Montana. — The mining camp of Butte (29-31), which is 
not only the greatest producer of copper in the world, but 
in which one mine, the Anaconda, yields one seventh of the 
entire world's supply, lies in the central part of the Rocky 




Fig. 52. — Map showing distribution of copper ores in United States. Adapted 
from Ransome, Min. Mag., X: 1. 



Mountain region. The ore-bearing veins occur in an older 
hornblendic granite, known as the Butte granite, found chiefly 
in the eastern part of the district, and which is cut by the 
acid Bluebird granite or aplite, that forms dikes and small 
masses in this region. Both of these granites are intersected 
by dikes of quartz porphyry of doubtful genetic relation to 
the ore bodies, although the latter are usually low-grade 
when bounded by either the porphyry or the aplite. The 
last stage of igneous activity consisted of the extrusion of 



COPPER 



283 








!2? w ^sUl»S*<J0.'i:'H B U T T E.3 . 





_J Pa/ - ALLUVIUM AND WASH PLEISTOCENE 
|j?j^J Nri - INTRUSIVE RHYOLITE NEOCENE 
|H|1|{ Cip- APLITE / 



SILVER VEINS 

COPPER VEINS 



POST CARBONIFEROUS 



,v{ qr- GRANITE 



Fig. 53. — Map of Butte, Mont., district showing distribution of veins and geology. 
After Weed, U. S. Geol. Surv., Atlas Folio. 



284 



ECONOMIC GEOLOGY OF THE UNITED STATES 



rhyolite flows and ash beds, and dikes of the same rock also 
cut the silver veins of the region. 

The Butte district contains both silver and copper veins. 
The latter are found in an area about a mile long and one 

half mile wide, in the south- 
eastern part of the district, 
while the silver veins sur- 
rounding it are of much less 
importance. 

The granites are traversed 
by several systems of joints 
and shear planes, and the ore 
has not only been deposited 
in them, but has replaced 
the wall rock as well. The 
veins are of varying age, the 
larger and richer ones hav- 
ing been broken, reopened, 
and even displaced by fault- 
ing, and a careful study of 
the district has shown four 
separate periods of fracture, 
in three of which ores have 
been formed. 

In the earliest, the vein 
filling, which was the result 
of replacement in sheeted granite, is quartz and pyrite with 
some copper. Later fracturing produced large masses of 
crushed granite, clay, etc., with boulders of ore, and this 
was sometimes added to by the deposition of enargite by 
later ascending solutions. The richest masses or bonanzas 




a. OXIDIZED ZONE 
6. CHALCOCITE 
C. ENARGITE 
d- PYRITE 
e. QUARTZ 
/. BORNITE 



CHALCOCITE 



H QUARTZ PORPHYRY 
~^J FAULT 

Fig. 54. — Section at Butte, Mont., show- 
ing mode of occurrence of ore. 
After Winchell, Eng. and Min. 
Jour., LXXVII: 782. 



Plate XVIII 




copper 285 

of glance found in some of the mines are of secondary 
origin. 

While the veins exhibit a curious uniformity of direction, 
most of them striking nearly east and west, and few of them 
departing more than 15° to 20° from the vertical, still they 
show considerable variation in width, ranging from a few 
feet to 50, or even 150 where the altered country rock is 
impregnated with glance. Unfortunately, the complexity of 
the veins and uncertainty of boundaries has given rise to 
much costly litigation in the district. 

The common vein minerals are pyrite, chalcocite, enar- 
gite, and bornite, with small amounts of chalcopyrite and 
covellite, in a quartzose gangue. Others existing in sub- 
ordinate quantities are tetrahedrite, tennantite, and argen- 
tite. The chalcocite is always of secondary character. 

The average composition of first-class ore in Butte in 
1902 was: Cu, 11.4 per cent; Fe, 16.6 per cent; Zn, .3 per 
cent; S, 22.6 per cent; As and Sb, 1.4 per cent; A1 2 3 , 7.9 
per cent; insoluble, 44.7 per cent; Si0 2 , 38.2 per cent; Ag, 
oz. 5.2; Au, oz. .04. Second-class ore averages: Cu, 5.2 
per cent; Fe, 16 per cent; S, 19.8 per cent; insoluble, 
5Q per cent; Ag, 3 oz. 

Gold is quite universally distributed through the ores, 
though in very small amounts, forming 3 per cent of the 
values in the copper bullion. Small amounts of arsenic, anti- 
mony, bismuth, tellurium, selenium, and nickel have been 
found, and manganese is widespread in the silver veins, 
though wanting in copper-bearing ones. Zinc is not limited 
in distribution, but is more abundant in the silver veins. 

The deposition of the ores is considered by Weed to be 
due to aqueous alkaline solutions, which have probably 



286 ECONOMIC GEOLOGY OF THE UNITED STATES 

leached the metals from the granite at considerable depths. 
These solutions, which came up in the fissures, were hot, 
but not necessarily under pressure. Where the fissures 
were open they were filled with ore, and where narrow, 
replacement of the walls occurred, so that the vein matter 
shades off into the country rock. Since their formation 
faulting has occurred, usually parallel to the vein. The 
entrance of meteoric waters into the vein has carried much 
ore downward, resulting in a richer zone below even the 
zone of oxidation, and showing bornite, chalcocite, and 
covellite as a result of this; some of these have been 
derived from the breaking up of the pyrite. It has been 
found that these bonanza bodies of secondary origin pass 
downward into lower-grade ores. Most of the ores are 
put through a process of mechanical concentration before 
being sent to the smelter. The vertical limits of the ore 
have not yet been determined, but certain silver mines 
have reached a depth of 1450 to 1500 feet, while most of 
the copper mines have gone to 1000 or 1500 feet. 

The history of this mining camp is full of interest. Butte in 1864 
was a gold camp, but difficulties in working the gravels directed atten- 
tion to the mineral-vein outcrops, and unsuccessful attempts were made 
to work their copper and silver contents, so that it was not until 1875, 
following a period of quiescence, that the discovery of rich silver ore 
in the Travona lode revived the mining industry of Butte. In 1877 
several silver mines were opened, followed by others ; bnt this did not 
last many years, for with the drop in the price of silver many mines 
closed, although one, the Bluebird, had produced 2,000,000 ounces of 
silver from 1885 to 1892. 

The copper mines were worked to only a limited extent at first, 
and the industry did not assume permanence until 1879-1880, when 
matte smelting was introduced. In 1881 the Anaconda mine, which 



copper 287 

was first worked for silver, began to show rich bodies of copper ore, 
and since then the output of copper has steadily increased, there being 
a number of large smelting plants distributed between Butte, Ana- 
conda, and Great Falls. 

Up to the end of 1896 the commercial value of the copper pro- 
duced was about $330,000,000. This greatly exceeds the total output 
of Leadville, and nearly equals the famous Comstock lode. W. H. 
Weed has estimated that up to January 1, 1897, the district had 
yielded 500,000 ounces of gold, 100,000,000 ounces of silver, and 
1,600,000,000 pounds of copper. In 1887 Butte passed the Lake Superior 
District in the production of copper, and has kept ahead of it ever since, 
having in 1903 produced 38.9 per cent of the United States produc- 
tion. 

COPPER LODES IN CONGLOMERATE 

_ AND AMYG DALOID LAYERS 

■^— ~ — 7^— — ^T " . .-" ~~ '.-- -.""--•.-- FAULT OR CL FF I 

< ' e $'<i>cri»r 

^ . -<i>^ ■.'•. ~ - . • ■"- •■"^— _ 

.. - '■'. ' ■-■:■ '.'■ 



>-.JGONGLP.MERATE>^/^, '///////&//, 




1 <> MILE S .NTERBEDDED LEAVERS OF CONGLOMERATE —SOUTH 45' EAST 

GEOLOGICAL CROSS-SECTION OF THE COPPER MINING REGION 



Fig. 55. — Section across Keweenaw Point. After Richard. 

Michigan (2,24-26). — This region, which was discovered 
in 1830 by Douglas Houghton, a mining engineer, has 
become one of the most famous, and for some years one 
of the leading, copper-producing districts of the world. 

The rocks of the region, known as the Keweenaw series, 
consist of steeply northwesterly dipping, interbedded lava 
flows, sandstones, and conglomerates. These form a belt 
from 2 to 6 miles wide, which extends from Houghton to 
the end of the Keweenaw peninsula, and rises as a ridge 
from 400 to 800 feet above the lake, being flanked on 
either side by Potsdam sandstone (Fig. 55} . 

The ore, which is native copper, and is occasionally asso- 
ciated with native silver, occurs (1) as a cement in the 



288 



ECONOMIC GEOLOGY OF THE UNITED STATES 



conglomerate of porphyry pebbles or replacing the latter; 
(2) as a filling in the amygdules of the lava beds; (3) as 
masses of irregular and often large size, in veins with 
calcitic and zeolitic gangue. 

The veins, which cut both the igneous and sedimentary 
rocks, have yielded much copper in former years, and the 
large masses obtained from them have made the region 
famous; but at the present time about 75' per cent of the 
production comes from the Calumet conglomerate, while 



_i _*_'_'_' -.' —■« _'_'__' _i_J -^r^^^-'o^^X^^i^X:, 




*•■-"•■ I •*,- ■• ■ -j," " -— - *■ _ . , ' 



Fig. 56. — Section showing occurrence of amygdaloidal copper, Quincy mine, 
Mich. After Richard, Eng. and Min. Jour., LXXVIII: 626, 1904. 

the balance comes from two other copper-bearing conglom- 
erates known as the Albany and the Allouez, and from 
the ash-beds and amygdaloids, whose gas cavities are filled 
with a mixture of native copper, calcite, and zeolites. 

A curious and hitherto unexplained feature is the irregu- 
lar distribution of the copper in the different beds. Thus 
the Calumet conglomerate carries practically no ore outside 
of the Calumet and Hecla ore shoot which is three miles long, 
12-15 feet thick, and has been mined to a depth of 5000 feet. 

Various theories have been brought forward to account 
for the origin of the copper ores in this region. 



copper 289 

That it is not a true contact deposit is shown by the fact 
that the amygdules in the diabase, the fissure veins, and the 
crevices in the broken pebbles are rilled with copper, show- 
ing a subsequent deposition. The diabase was looked upon 
by PumpelJy (25 h) as a possible source of the ore, and since 
its extensive alteration was no doubt accompanied by the 
oxidation of protoxides, this might account for the reduc- 
tion of copper mineral to the native or metallic condition, 
it being known that ferrous salts may precipitate metallic 
copper (1). More recently Lane (25 a) has suggested that 
the ores were deposited chiefly by descending meteoric 
waters, because the more productive mines seem to be 
situated under the highest portions of the point, and hence 
were in the path of the descending waters. Such a theory, 
however, requires the topography to have been the same 
when the copper was deposited as it is now. 

Although these deposits have been worked in prehistoric 
times, as evidenced by copper implements and ornaments 
found in the mines, the famous Calumet and Hecla Mine 
was not opened up until 1846. In 1847 Michigan pro- 
duced 213 long tons of the total United States production 
of 300 tons of copper. Since 1863 the annual output has 
exceeded 1000 tons and has gradually and steadily increased, 
reaching 85,893 long tons in 1903, having a market value of 
120,269,000. 

The ores from this district, which are known as Lake ores, 
are all of low grade, some running as low as .55 per cent 
native copper. Owing, however, to the brittle character of 
the gangue and the malleability of the ore, as well as their 
difference in specific gravity, it is possible to separate the 
two quite thoroughly by crushing in stamps and concentrat- 



290 ECONOMIC GEOLOGY OF THE UNITED STATES 

ing by jigs, tables, etc. This concentrated material is then 
refined electrolytically. 

Arizona (8-16). — This territory ranks third as a producer 
of copper ores in the United States, and differs from most 
other copper-producing localities in supplying chiefly ores 
of oxidized character ; in fact, from 1880 to 1895 Arizona was 
the only copper area in the world whose ores were exclusively 
oxidized. 

The territory contains four important districts, all lying 
within the mountain region, and which in the order of their 
importance are, (1) Bisbee or Warren, (3) Jerome or Black 
Range, (3) Clifton, Morenci, or Copper Mountain, and (4) 
Globe. In all except the second the modes of the ore occur- 
rences possess certain similarities. 

Bisbee or Warren District. — This district (11,15), which 
contains the famous Copper Queen Mine, lies on the eastern 
slope of the Mule Pass Mountains, but a short distance from 
the Mexican boundary. The section at that locality involves 
strata from pre-Cambrian to Cretaceous age, with an im- 
portant unconformity between the Carboniferous and Cre- 
taceous (Fig. 57). Prior to the deposition of the latter the 
rocks had been broken by numerous faults, one of these, the 
Dividend fault, being specially prominent in forming one 
boundary of the ore-bearing area. This was followed by 
intrusions of a granitic magma forming dikes, sills, or 
irregular stocks, which have metamorphosed the Carbon- 
iferous limestones, with the production of characteristic 
contact minerals. 

The ore bodies, which are generally developed in the zone 
of metamorphic silicates surrounding the porphyry, as well as 
sometimes outside of it, form large, irregularly distributed, 



COPPER 



291 



but rudely tabular masses, which are generally parallel to 
the limestone bedding. As now found they consist of oxi- 
dized ores, such as malachite, azurite, and cuprite, above, 
which pass at variable depths into unaltered sulphides ; but 
between the two, or at least never far from the effects of 




Bed nodular shale* with crews- 
bedded, buff, tawny, and red 
sandstones. A Tew beds of im- 
pure limestone near base. Un- 
comformabl; overlain by flona 
tile Quaternary deposits. 



rhiL-k-bedded, hard. gray, fossil- 



BufT, tawny and red sandstones 
and dark-red shales, with an 
thin bed of impure 



Horita formation. 1,800 feet. 



angular pebble* chief] v aehid 

■ 
1 _^ - — - ' '- 



Chiefly I ighr-gray 

in bed* of 

Contains abundao 

Cut by granite-porphyry, 



i! :■- : . .. - '■■ v . -. 

" nestoDc. Contain* aim nd ant 
noid stems. Cut by granite 

porphyry. 



Trim-bedded, impure, cherty 
limestones. Cut by granite- 
porphyry. 



Seri cite- schists. Cut by | 
and granite-porphyr 



Cintnra formation, 1,800 feet 
plus unknown thickness. 



:t-ne. 6"J fett. 



Glance conglomerate, 
25 to 5uu feet. 



Kaco limestone, 3, ,000 feet 
removed by pre- Cretaceous 



ne. 310 feet 
n conformity. 



.Abrigo limestone. -TO feet. 



Bolsa quartxite, 430 feet. 
Great i 



GENERALIZED COLUMNAR SECTION OF THE ROCKS OF THE B1SBEE QUADRANGLE. 

Fig. 57. — Geological section at Bisbee, Ariz. After Ransome. U. S. Geol. Surv., 

Prof. Pap. 21. 

oxidation, masses of massive or sooty clialcocite are fre- 
quently found. 

The ore-bearing solutions are believed to have been stimu- 
lated by the porphyry and to have risen from an unknown 
source, but although they may have followed some of the 



292 



ECONOMIC GEOLOGY OF THE UNITED STATES 




GRANITE MINERALIZED CHALCOCITE OXIDIZED MINERALIZED CARBONIFEROUS 
PORPHYRY GRANITE COPPER LIMESTONE LIMESTONE 

PORPHYRY ORES 



Fig. 58. 



Generalized section of ore bodies at Bisbee, 
Ariz. After Ransome. 



fault fissures, the ore, which originally consisted of pyrite, 
chalcopyrite, and occasionally sphalerite, owes its deposition 
to metasomatic replacement in the limestone. As originally 
formed, the deposits contained too little copper to make 

them of commer- 
cial value, but they 
have been subse- 
quently enriched 
by concentration 
due to weather- 
ing in the upper 
part, and second- 
ary deposition of 
chalcocite in the 
underlying zone. 
Indeed it is said that nearly all the bodies of workable 
sulphides owe their value to its presence. 

The gossan of some of the ore bodies forms prominent 
ferruginous ledges, and while these rarely show surface in- 
dications of copper, still experience has shown that they are 
connected with underlying ore bodies; however, many of 
the latter have no outcrops. 

Although always important, this region assumed great 
prominence in 1903, due to the opening and extensive de- 
velopment of new ore bodies of great extent. 

Jerome District. — This was the leading copper-producing 
district of Arizona for 1897 to 1900 inclusive, but then 
dropped to second place. The mode of occurrence of the 
ore differs markedly from that noted in other areas. It is 
bornite and chalcopyrite, which is associated with a sheared 
dike and fills fissures and impregnates the slate rock. 



Plate XIX 




Fig. 1. —Smelter of Arizona Copper Co., Clifton, Ariz. After Church, Mia. Mag. 

X: 2, 1904. 




Fig. 2. — View of Bingham Canon, Utah. After Boutioell, U. S. Geol. Surv., Prof. 

Paper 38, 1905. 



copper 293 

Clifton District. — In this district (12, 13), which ranks 
third among the Arizona copper districts, the conditions 
are in part similar to the Bisbee district in so far as the 
geologic section and the intrusion of porphyry and granite 
into the Palaeozoic sediments is concerned. They have 
likewise been broken by extensive fracturing and faulting, 
the faults sometimes having a throw of 1000 to 1500 feet, 
and there was also an extensive flow of Tertiary eruptives. 
The ore bodies differ from the Bisbee ones, however, in 
point of origin, being true contact deposits, the porphyry 
by contact influence having produced great masses of garnet 




Fig. 59. — Section of Morenci district. P, porphyry; S, unaltered sediments; 
F, fissure veins; M, metamorphosed limestone and shale; O, contact meta- 
morphic ores ; R, disseminated chalcocite. After Lindgren, Eng. and Min. 
Jour., LXXVIII: 987, 1904. 

and epidote in the Carboniferous limestones ; and wherever 
alteration has not masked the phenomena, the metallic 
minerals, magnetite, pyrite, chalcopyrite, and sphalerite, are 
found accompanying the contact silicates, and often inter- 
grown with them in such a manner as to leave no doubt 
concerning the contact origin of the ores and the porph} T ry 
as their source. The concentration and commercial value 
of the ores is due, however, to later processes intimately 
connected with weathering. This has produced malachite 
and azurite in the gossan, but some of the copper has been 
carried to lower levels and precipitated as chalcocite. The 
sphalerite has been removed in solution as zinc sulphate, and 
the magnetite and garnet have yielded silica and limonite. 



294 ECONOMIC GEOLOGY OF THE UNITED STATES 

The ore deposits in the limestone are irregular or tabular, 
due to the accumulation of the minerals along bedding 
planes, but in addition, fissure veins, cutting through many 
of the rocks, and of later age than the porphyry, are found. 

Grlobe District (14). — While the most important deposits 
here occur in limestone, near the contact with granite and 
trachyte, still others are found as fissure veins in sand- 
stone (Old Dominion Mine), or in slate and gneiss, or 
even veinlets in gneiss ; the ores are largely oxidized. 
The output of this district, which has been the least actively 
worked of any, though small for several years, increased 
greatly in 1901. 

Appalachian Region (42, 43). — The existence of copper 
in the Appalachian belt has been known for a number of 
years, but the copper-mining industry has not been active. 
The early attempts to work the deposits were chiefly to 
obtain both gold and copper, and resulted in failure, due 
chiefly to the low market values of copper ; hence for many 
years the deposits, with few exceptions, have been but 
little worked, and it is only recently that a demand for 
the metal and cheaper metallurgical treatment have revived 
copper mining. 

The deposits in many cases occur in metamorphic rocks 
scattered over a wide belt, but five important types are 
recognizable (42) : — 

1. True fissure veins, filled with quartz and copper, the 
vein crossing or conforming to the banding of the schists, 
and replacement of the wall rock being rare. The ores 
are bornite, with a little chalcopyrite and iron pyrite. The 
deposits at Virgilina, Virginia, belong in this group. 

2. True fissure veins with auriferous quartz, chalcopyrite, 



copper 295 

and pyrite formed chiefly by replacement. The fissures 
are usually found along sheeting planes, and the deposits 
at Gold Hill, North Carolina, are taken as a type of this 
group. 

3. Pyrrhotite veins of the Ducktown type (36-38), filling 
true fissures, and consisting chiefly of pyrrhotite and pyrite 
with a little qnartz. The ore has been formed by the 
replacement of a zone of sheeted rock, which was com- 
posed chiefly of metamorphic minerals, such as garnet, 
actinolite, epidote, pyroxene, etc., these latter being the 
products of alteration of a calcareous shale. The Duck- 
town ore body represents a type forming a belt extending 
all the way from Vermont to Alabama. They all show a 
gossan which can be mined for iron ore, while under this 
there is a zone of black copper, the result of local enrich- 
ment, which passes into the sulphide ore below. The 
copper is richest in those portions where the pyrrhotite 
predominates. The Ducktown ore, which has been worked 
for a number of years, averages 3.5 per cent copper as it 
comes from the mine. Some of the chambers are from 50 
to 150 feet across, and from 25 to 150 feet high without 
timbering. 

The great gossan lead of Virginia and the copper de- 
posits of Ore Knob, North Carolina, also belong to this 
type. 

4. The Catoctin type, representing segregations of native 
copper, copper oxides, and carbonates along shear zones in 
altered igneous rocks of Algonkian age, the ores extend- 
ing below ground water level. They are found at a num- 
ber of localities in the Appalachian and Piedmont plateau 
districts, usually in the Catoctin schist. The ore shows 



296 ECONOMIC GEOLOGY OF THE UNITED STATES 

on the outcrop, but does not extend usually more than 50 
to 60 feet below the surface. It is supposed to have been 
leached out of the vein walls. Occurrences of this type 
occur in Green County, Virginia. 

5. Deposits of native copper along the contact of diabase 
and sandstone. These have been found in New Jersey (32, 33), 
but are unimportant, although the mines have been worked 
from time to time. Similar occurrences have been reported 
from Pennsylvania (34, 35) and Connecticut. 

Utah. — This state ranks fourth among the copper-produc- 
ing regions of the United States. The most important dis- 
trict is that of Bingham Canon (44), in the Oquirrh range, 
southwest of Salt Lake City, and is unique in that it includes 
the oldest mining claim in the state. It moreover differs 
from the other important copper mining localities in the 
country, in having a considerable quantity of gold, silver, 
and lead associated with the copper. 

The rocks of this district include: (1) a great thickness 
of sedimentaries of Carboniferous age and divisible into a 
lower member consisting of massive quartzite with several 
interbedded limestones which carry most of the ore bodies 
in the camp, and an upper member of quartzite with 
black calcareous shales, sandstones, and impure limestones; 
(2) igneous rocks, which have pierced the entire series of 
sedimentaries, forming dikes, sills, or laccoliths, and consist- 
ing either of a type between diorite porphyrite and mon- 
zonite, which is closely associated with the ore bodies, or an 
andesite, having no relation to the ores. 

Folding, fracturing, and faulting have greatly complicated 
the structural relations of this region. 

The ores form lenses in the limestone, which lie roughly 



coppek 297 

parallel to its bedding, or occupy fractures or fissure zones. 
Copper, lead, silver, and gold may occur in either, but the 
copper rather favors the lenses, and the lead and silver the 
fissures. 

The mining operations have been based in turn on the 
oxidized gold ores, carbonate ores of lead and copper, sul- 
phides of lead, and finally sulphides of copper, which now 
constitute the mainstay of the district. These copper sul- 
phides are cupriferous pyrite, chalcopyrite, black sulphides 
(probably tetrahedrite), and chalcocite with a little galena, 
zinc, and siliceous gangue. The pyrite, which is widespread 
in the district, forms immense replacement bodies in the 
limestone, but is of secondary importance in the fissure zones. 
The Bingham ores are of low value, and bonanzas are rare ; 
indeed, the copper ores can often only be profitably worked 
because of their gold, lead, and silver contents. 

California. — California (17, IS, 2) in 1903 was fifth in the 
list of copper-producing states, and owes its position to the 
output from Shasta County in the northern part of the state. 
This region lies at the northern end of the Sacramento Valley, 
and contains a series of sedimentary rocks, ranging from 
Devonian to Miocene and pierced by igneous intrusions. 
Folding, faulting, and shearing are common. The ore 
is found either : (1) as sulphide deposits in contact zones, 
between diabase dikes and Carboniferous limestones; or (2) as 
bodies of sulphides, in shear zones, the latter having been 
mineralized with the development of irregular ore bodies of 
variable size. The ores are rare generally in the metamor- 
phosed igneous rocks. Superficial alteration has produced 
a gossan which may show a thickness of as much as 100 feet 
at some localities (Iron Mountain). 



298 



ECONOMIC GEOLOGY OF THE UNITED STATES 



The important districts are the Iron Mountain and Bully 
Hill. In both, the ores are chalcopyrite and pyrite, but 
that from the latter district also contains some bornite and 
chalcocite. An analysis of the Iron Mountain ore gave, Cu, 
7.45 per cent; S, 45.60 per cent; Fe, 36.97 per cent; Zn, 

3.41 per cent; Si0 2 , 5.62 per cent ; 
A1 2 3 , 1.57 per cent; Moisture, 
0.88 per cent. This is probably 
higher than the average in cop- 
per. 

Copper deposits are also known 
in other parts of California (17). 

Other Occurrences. — Colorado 
has few copper mines proper, but 
many of the ores mined in the 
state carry copper, and it is util- 
ized by lead smelters as a carrier 
in the extraction of other metals. 




METARHYOLITE 



OXIDIZED ORES 



m 

EEL 

Fig. 60. — Section of ore body at 
Bully Hill, Calif. After Diller. 



EHenr,chedsulph,des Copper is mined in New Mexico 
and Idaho, the Seven Devils Dis- 
trict of the latter state being well 
known (23). The Grand Encampment district of southern 
Wyoming (50) has also supplied more or less ore, and a small 
amount is mined in Missouri (28). Copper has been found 
at several localities in Alaska (4-7), but no shipments were 
made prior to 1903. 



Uses of Copper. — Since prehistoric times copper alloyed 
with tin has been used in various parts of the world for the 
manufacture of bronze. Thus it was used for this purpose 
in Homeric times, and it is found in the lake dwellings of 



copper 299 

Switzerland. The bronze found in Troy contains a very little 
tin, and since this metal is not found in the excavations in 
the West, it seems probable that the bronze was made in 
Asia, perhaps in China or India, by some secret process and 
imported to the western countries. 

By an alloy of copper and tin, although both metals 
are soft, a comparatively hard metal is produced. The 
properties of this alloy, bronze, vary greatly according 
to the proportions of the two metallic constituents, and 
these vary with the use for which the alloy is intended. 
United States ordnance is 90 per cent copper and 10 per 
cent tin, while ordinary bell metal is about 80 per cent 
copper, though the percentage varies with the tone re- 
quired. Statuary bronze is generally an alloy of copper, 
tin, and zinc ; and, in these various bronzes, the color 
varies from copper-red to tin-white, passing through an 
orange-yellow. 

An alloy of copper and zinc produces brass, which is found 
of so much value for small articles used in building and for 
ornamental purposes in machinery. Copper is also used in 
roofing and plumbing. 

A large supply of this metal is made into copper wire, 
and the most important present use of copper is in electricity, 
for which its high conductivity especially fits it for the 
transmission of electric currents. 

Production of Copper. — The production of copper in the 
United States has increased steadily and rapidly in the last 
fifty years, placing the United States in the lead of the 
world's copper producers. This increase can be seen from 
the table given below : — 



300 



ECONOMIC GEOLOGY OF THE UNITED STATES 



Production of Copper in United States from 1845 to 1903 



Year 


Production 
Long Tons 


Year 


Production 
Long Tons 


1845 


100 


1885 


74,052 


1850 


650 


1890 


115,996 


1855 


3,000 


1895 


169,917 


1860 


7,200 


1900 


270,588 


1865 


8,500 


1901 


268,782 


1870 


12,600 


1902 


294,423 


1875 


18,000 


1903 


311,627 


1880 


27,000 







Production of Copper in the United States by States 
(In pounds) 



Source 



Arizona 

California . . . . 
Colorado 1 .... 
Lake Superior . . . 
Montana . . . . . 
New Mexico ... 

Utah 

Eastern Atlantic States 
All others . . . . 



1901 



130,778,511 

33,667,456 

9,801,783 

156,289,481 

229,870,415 

9,629,884 

20,116,979 

6,860,039 

4,526,341 



1902 



119,944,944 

25,038,724 

8,422,030 

170,609,228 

288,903,820 

6,614,961 

23,939,901 

13,599,047 

1,935,989 



1903 



147,648,271 

17,776,756 

4,158,368 

192,400,577 

272,555,854 

7,300,832 

38,302,602 

13,855,612 

3,546,645 



Of the several producing states Montana has for some 
years been the first, with Michigan second and Arizona 
third. The marked decrease of Montana in 1903 was due 
to litigation and labor troubles. 



1 Including copper smelters purchasing copper ore and mattes in the open 
market, sources not known. 



COPPER 301 

World's Production of Copper in Long Tons 

Country 1903 

Chile 30,930 

Germany 21,205 

Japan 31,360 

Mexico 50,480 

Spain and. Portugal 49,740 

United States 311,627 

All others 89,739 

The total value of the imports of copper (including ore, 
matte, and manufactured copper) in 1903 was 120,441,977, 
while the total value of the exports covering the same class 
of materials was §44,365,155. 

REFERENCES ON COPPER 

General. 1. Biddle, Jour. GeoL, IX: 430, 1901. (Origin.) 2. Weed, 
Min. Mag., X:185, 1904. (United States.) 3. Winchell, Geol. 
Soc. Amer, Bull. XIV: 269, 1903. (Origin.). — Alaska : 4. Brooks, 
Eng. and Min. Jour., LXXIY : 13. (Tanana and Copper River 
regions.) 5. Mendenhall and Schrader, U. S. Geol. Surv., Bull. 
213 : 141, 1903. (Mt. Wrangell region.) 6. Rohn, U. S. Geol. Surv., 
21st Ann. Rept., 11:393, 1900. (Chitina River and Skolar flits.) 

7. Schrader, U. S. Geol. Surv., 20th Ann. Rept., VII: 341, 1900. 
(Prince William Sound and Copper River district.) — Arizona : 

8. Blandy,Eng.andMin. Jour., LXIV: 97, 1897. (Ariz.) 9. Church, 
Amer. Inst. Min. Engrs., Trans. XXXIII: 13, 1903. (Tombstone 
district.) 10. Douglas, Min. Indus., VI : 227, 1898. 11. Douglas, 
Amer. Inst. Min. Engrs., Trans. XXIX : 511, 1900. (Copper Queen 
Mine). 12. Lindgren, U. S. Geol. Snrv., Bull. 213 : 133, 1903. (Clif- 
ton district.) 13. Lindgren, Amer. Inst. Min. Engrs., Trans. XXXV, 
1905. (Clifton district.) 14. Ransome, U. S. Geol. Surv., Prof. 
Paper 12, 1903. (Globe district.) 15. Ransome, U. S. Geol. Surv., 
Prof. Paper 21, 1904. (Bisbee district.) 16. Wendt, Amer. Inst. Min. 
Engrs., Trans. XV: 25, 1887. — California: 17. Aubury, Calif. State 
Mining Bureau. Bull. 23, 1902. 18. Diller, Eng. and Min. Jour., 
LXXIII:857, 1902. (X. Calif.) — Colorado : 19. Emmons, Tenth 
Census, XIII : 68, 1880. (Gilpin Co.) 20. Spencer, U. S. Geol. 
Surv., Bull. 213:163, 1903. (Pearl, Colo.) 21. Emmons, U. S. 
Geol. Surv., Bull. 260:221, 1905. (Red Beds, Colo, plateau.) — 



302 ECONOMIC GEOLOGY OF THE UNITED STATES 

Georgia: 22. Weed, U. S. Geol. Surv., Bull. 225:180, 1904.— 
Idaho: 23. Lindgren, Min. and Sci. Pr., LXXVI1I : 125, 1899. 
(Seven Devils district.) — Michigan: 24. Irving, U. S. Geol. Surv., 
Mon. V, 1883, also 3d Ann. Kept. : 89, 1883. 25. Lane, Amer. 
Geol., XXII : 251, 1898. (Magmatic differentiation in copper 
rocks.) 25 a. Lane, Mich. Miner, Jan.-Feb., 1904. 25 b. Pumpelly, 
Mich. Geol. Surv., I, pt. 2 : 14. 26. Rickard, Eng. and Min. Jour., 
LXXVIII:585, 625, 665, 745, 785, 865, 905, 1025, 1904. — Missouri : 
27. Nicholson, Amer. Inst. Min. Engrs., X : 444, 1881. (St. Genevieve 
district.) 28. Bain and Ulrich, U. S. Geol. Surv., Bull. 260 : 233, 1905. 
(General.)— Montana: 29. Weed, U. S. Geol. Surv., Bull. 213:170, 

1903. (Butte.) 30. Winchell, Eng. and Min. Jour., LXXVII:782, 

1904. 31. Winchell, Geol. Soc. Amer., Bull. XIV: 269, 1903.— New 
Jersey: 32. Kiimmel, N.J. Geol. Surv., Ann. Kept., 1899:171, 1900. 
33. Weed, U. S. Geol. Surv., Bull. 225 : 187, 1904. (Griggstown.) — 
Pennsylvania: 34. Bailey, Eng. and Min. Jour., XXXV : 88, 1883. 
(Adams County.) 35. Lyman, Jour. Franklin Inst., CXLYI:416, 
1898. (Bucks and Montgomery counties.) — Tennessee : 36. Hen- 
rich, Amer. Inst. Min. Engrs., Trans. XXV : 173, 1896. (Ducktown.) 
37. Kemp, Amer. Inst. Min. Engrs., Trans. XXXI : 244, 1902. 
(Ducktown.) 38. Weed, Amer. Inst. Min. Engrs., Trans. XXX : 
449,1901. (Southern Appalachians.) — Texas: 39. Schmitz, Amer. 
Inst. Min. Engrs., Trans. XXVI : 97, 1897. (Permian ores.) — 
United States : 40. Douglas, Amer. Inst. Min. Engrs., Trans. 
XIX: 678, 1891. 41. Stevens, Copper Handbook, published an- 
nually at Houghton, Michigan, by the author, $5. 42. Weed, U. S. 
Geol. Surv., Bull. 213 : 181, 1903 (Appalachians) ; and Bull. 260 : 217, 

1905. (E. U. S.) 43. Weed, U. S. Geol. Surv., Bull. 260 : 211, 1905. 
(U. S. localities and industry.) — Utah: 44. Boutwell, U. S. Geol. 
Surv., Bull. 213 : 105, 1903. (Bingham.) Also U. S. Geol. Surv., Prof. 
Paper 38, 1905. — Vermont : 45. Weed, U. S. Geol. Surv., Bull. 225: 
190, 1904. 46. Smyth and Smith, Eng. and Min. Jour., April 28, 
1904. — Virginia : 47. Watson, Geol. Soc. Amer., Bull. XIII: 353, 
1902. (Virgilin a district.) — Wisconsin: 48. Grant, Wisconsin Geol. 
and Nat. Hist. Surv., Bull. No. 6, 1901. (Douglas Co.) — Wyoming : 
49. Kennedy, Eng. and Min. Jour., LXVI : 640, 1898. 50. Spencer, 
U. S. Geol. Surv., Bull. 213 : 158, 1903. (Encampment region.) 



CHAPTER XVI 

LEAD AND ZINC 

These two ores can hardly be treated separately for the 
reason that they occur so often associated with each other ; 
the combination of lead and silver, of importance in the 
Rocky Mountain region, is treated under a separate head. 

Ores of Lead. — The ores of lead, together with their com- 
position and the percentage of lead which they contain, are : — 

Galena, PbS, 86.4; 

Cerussite, PbC0 3 , 77.5; 

Anglesite, PbS0 4 , 68.3; 

Pyromorphite, Pb 3 P 2 8 + J PbCl 2 , 76.36. 
Of these, galena is the commonest, while the other two are 
usually found in those localities where superficial oxidation 
of the ore deposit has taken place. The lead obtained from 
argentiferous ore is commonly spoken of as desilverized or 
hard lead, while that from non-argentiferous ones, such as 
those of the Mississippi Valley areas, is known as soft lead. 

Ores of Zinc. — The ores of zinc, together with the per- 
centage of zinc they contain, are : — 
Sphalerite, ZnS, 67 ; 
Smithsonite, ZnC0 3 , 51.96; 
Calamine, H 2 Zn 2 Si0 5 , 54.2; 
Zincite, ZnO, 80.3; 
Willemite, Zn 2 Si0 4 , 58.5; 

Franklinite (FeZnMn)0(FeMn) 2 3 , composition vari- 
able but containing about 51.8 Fe and 7.5 Mn. 
303 



304 ECONOMIC GEOLOGY OF THE UNITED STATES 

Of these ores, sphalerite (also known as blende, jack, or 
black-jack) is by far the most important, except in northern 
New Jersey, where it is practically lacking and franklinite 
and willemite abound. With few exceptions, zinc is con- 
stantly associated with lead, and at times, as in portions of 
the Cordilleran region, carries silver or even gold. 

Calcite, dolomite, and pyrite are common gangue minerals 
of non-argentiferous lead, and zinc ores, and others may 
occur at certain localities. In the argentiferous ores, quartz 
is probably the commonest gangue mineral, but there may 
be other less important ones. 

Iron, lead, and manganese are not uncommon impurities 
in zinc ores, and those of Missouri contain small amounts of 
cadmium, but this is not injurious, as it is more volatile than 
the zinc and easily driven off by heat. 

Argentiferous lead ores sometimes contain antimony, 
arsenic, and iron as impurities. Those of the Appala- 
chians, which are practically non-argentiferous, are free from 
most of these. 

Neither lead or zinc ores are restricted to any one forma- 
tion, but the majority of economically valuable deposits of 
these metals, without silver, gold, or copper, are found in the 
Paleozoic formations, although a few are known in pre- 
Cambrian rocks. They exist as disseminations, chamber 
deposits, as filling in brecciated zones, in gash veins and 
replacements. While the metallic contents of the ore as 
mined is often low, still, owing to the great difference in 
gravity between ore and gangue (excepting pyrite), it is 
often possible to separate them by mechanical concentration ; 
and for the zinc ores magnetic separation has been success- 
fully tried. 



LEAD AND ZINC 



305 



Superficial Alteration of Lead and Zinc Ores. — Galena is 
often altered near the surface to anglesite or cerussite. The 
former, however, is unstable in the presence of carbonated 
waters and changes readily to carbonate. Phosphates are 
developed in rare instances. 

Sphalerite, the common ore of zinc, is often changed super- 
ficially to smithsonite, hydrozincite, or calamine. Such oxi- 
dized ores are of greater value than unoxidized ones, because 




Fig. 61. — Map showing distribution of lead and zinc ores in United States. 
Adapted from Ransome, Min. Mag., X: 1. 

although carrying a lower percentage of zinc, they occur in 
a more concentrated form and yield more easily to metal- 
lurgical treatment. 

Distribution of Lead and Zinc Ores in the United States. — 
The occurrence of lead or zinc with gold, silver, and copper 
is confined chiefly to the Cordilleran region, and shows a 
most varied mode of occurrence; but commercially valuable 
deposits of lead alone, or lead and zinc, are confined to the 



306 



ECONOMIC GEOLOGY OF THE UNITED STATES 



Mississippi Valley, while those of zinc alone or with little 
lead are restricted to the Appalachian region as seen 
below. 



Lead Alone. Appalachian Belt (11, 25, 29). — Lead (some- 
times argentiferous) occurs at a number of localities from 
Maine to Georgia, filling small veins in metamorphic rocks, 
and the deposits have at various times aroused temporary 
interest. There is no likelihood of their ever becoming im- 
portant producers, although exciting rumors regarding them 
are occasionally circulated. 

Southeastern Missouri (12, 18, 19). — This area forms a 
subdistrict of the Ozark lead and zinc region, to be 

mentioned later. 
The galena is 
found in Lower 
Silurian lime- 
stones, the larger 
lead deposits oc- 
curring in mas- 
sive strata near 

Fig. 62. — Generalized section of Southeastern Missouri the base, called 
lead region. After Bain. gt< Joseph Hme _ 

stone, while others with a little zinc are in the cherty Potosi 
limestone near the summit; the sandstone layers are barren. 
The ore forms great impregnations, but cavern or vein de- 
posits so common in other parts of Missouri are wanting 
in this region; while many small faults occur, the ore sel- 
dom favors them. The origin of these ores is treated under 
lead and zinc. The average ore runs from 6 to 8 per cent 
galena; when roughly handpicked, 10 to 12; and subse- 




POTOSI 
LIMESTONE I 



BROWN 

LIMESTONE 
JIN WHICH 
1THE ORE OCCURS 



LEAD AND ZINC 307 

quent jigging of the crushed ore brings the galena contents 
up to 60 or 70 per cent. 

The Missouri lead mines were worked at a very early date 
for making bullets, and their product is said to have been 
used during the Revolution. 

Desilverized Lead. — The important localities supplying 
this type of lead are described under lead-silver ores, but 
brief reference may be made to them here. Idaho is the 
most important producer, more than 96 per cent coming 
from the Coeur d'Alene district. In Utah much is ob- 
tained from the Park City district of Summit County, 
the Bingham Canon and Cottonwood districts of Salt 
Lake County, and the Tintic district of Juab County. 
Colorado's main supply is yielded by the Leadville mines 
in Lake County and the Aspen mines of Pitkin County, 
while smaller amounts are obtained from Creede, Lake 
City, Ouray, and Rico. (See Lead-Silver references, also 
map, Fig. 73.) (28.) 

Comparatively little lead is produced in the western states, 
except in the three mentioned above. 

As pointed out by Bain, the important lead ores of this 
region are closely associated with both igneous and sedi- 
mentary rocks. At Leadville, Aspen, and Park City the 
sediments are dolomites and limestones, and at Coeur d'Alene 
they are shales and quartzites. While the ores seem to favor 
igneous associations, still the larger bodies are found where 
both classes of rocks occur. 

Zinc Ores. — The zinc-producing regions of the United 
States are the eastern and southern states, the Mississippi 
Valley, and the Rocky Mountain region. 



308 ECONOMIC GEOLOGY OF THE UNITED STATES 

The ore from the different districts varies in grade, associa- 
tions and mode of occurrence. 

In tonnage terms, the main zinc-producing districts are 
the Joplin, Missouri, Sussex County, New Jersey, and 
Colorado. The Joplin ores are the main source of supply 
of the Kansas, Missouri, and Illinois smelters, but Colorado 
and even British Columbia ore is shipped to Kansas. 
Most of the New Jersey ore is used for zinc oxide, but 
smaller amounts are exported or used for spelter. 

Eastern and Southern States. — The localities where zinc 
alone occurs are Sussex County, New Jersey ; Saucon Valley, 
Pennsylvania ; and the Virginia-Tennessee belt. Of these 
the first is the most important, and the third yields a little 
lead. 

Sussex County, New Jersey (20-22). — The output of these 
mines is second in importance to those of the Mississippi 
Valley region. The district includes two general mining 
areas situated close together, the one called Mine Hill, at 
Franklin, and the other called Sterling Hill, at Ogdens- 
burg, two miles farther south, but not now worked. 

The ore-bearing minerals, which represent a unique type 
of occurrence, consist of franklinite, zincite, willemite, and 
calamine, the typical ore being a granular mixture of frank- 
linite and calcite, with zincite and willemite scattered 
through it. Manganese minerals are also present, thus giv- 
ing a combination of three common elements, viz., man- 
ganese, zinc, and iron. 

The average mineralogical composition of the Franklin 
Furnace ore (Ingalls) is franklinite, 51.92 ; willemite, 
31.58 ; calcite, 12.67 ; zincite, .52 ; other silicates, 3.31 ; 



LEAD AND ZINC 



309 



while the average chemical composition is : Fe 2 3 , 32.06 ; 
MnO, 11.06 ; ZnO, 29.35; CaC0 3 , 12.67; silica and in- 
soluble matter, 14.57. 

The ore body at both localities is interbedded with a 
white crystalline limestone of probably pre-Cambrian age, 
which in turn rests on gneiss. The Ogdensburg ore deposit 
forms a great hook, giving two veins apparently, and the 
ore body seems to be an impregnated streak of limestone ; 
while at Mine Hill the northerly pitching ore body is also 




Fig. 63. 



Model of Franklin zinc ore body. After Na&on, Amer. Inst. Mill. 
Engrs., Trans. XXIV l 127. 



a synclinal fold, whose southern end in addition appears 
to be doubled over into an anticline. In both cases the 
wall rock is heavily impregnated at the bends of the fold 
with franklinite and other minerals, while the ore bodies 
are pierced by intrusive rocks. The origin of these de- 
posits is of unusual interest, for they not only contain in 
abundance a number of zinc minerals rare or unknown 
elsewhere, but many other mineral species as well. No 
sulphides of either zinc or iron have been noted, to suggest 
a derivation from that source, and faults which might serve 
as ore channels are likewise lacking, consequently their 
origin is difficult to explain. 



310 



ECONOMIC GEOLOGY OF THE UNITED STATES 



Kemp (20) considers that the ore was probably deposited 
from solutions stimulated by intrusions of granite, and sub- 
sequently metamorphosed, but Wolff (21) suggests that they 
are contemporaneous in form and structure with the in- 
closing limestones, and hence older than the granites. The 
extent to which they have been metamorphosed has served 
to hide their original character, and theories regarding their 
possible origin have been largely speculative. 




Fig. 61. — Section of Bertha zinc mines, Wythe Co., Va., showing irregular 
surface of limestone covered by residual clay bearing ore. After Case, Amer. 
Inst. Min. Engrs., Trans. XXII: 520. 

These ore bodies are of some historic interest, having been prospected 
as early as 1640 and mined in 1774. The Mine Hill deposits were worked 
for iron ore as early as the beginning of the last century, the zinc mining 
having begun about 1840. The ores are now treated by magnetic sepa- 
rators, which remove the franklinite and garnet from the willemite and 
zincite, while the calcite is taken out by jigging. The zinc ores are used 
for metallic zinc and zinc white, and the manganese for Bessemer steel. 

Virginia-Tennessee Belt (32-35, 26, 27). — Zinc and some 
lead occur in a belt extending from southwest Virginia 
into Tennessee. The ores are intimately associated with 
Cambro-Ordovician limestone, and show two types, viz. : 
(1) secondary or weathered ores, including calamine, smith- 



LEAD AND ZINC 311 

sonite, and cerussite, which are concentrated in the residual 
clays next to the irregular weathered surface of the lime- 
stone (Pl. XVII, Fig. 2); and (2) primary ores, including 
sphalerite, galena, and some pyrite, belonging to the dis- 
seminated replacement breccia type, and which have been 
localized by ground waters along the crushed and faulted 
axes of the folds. The gangue minerals are chiefly calcite, 
dolomite, and some barite. Fluorite is known, and quartz 
may occur in the form of chert. One deposit only, in Albe- 
marle County, is found in schist, and is closely associated 
with igneous rocks. 

Pennsylvania (25 a). — The Saucon Valley deposits promised 
at one time to become prominent producers, but have not, 
owing more to geological conditions than actual scarcity of ore. 

Lead and Zinc Ores of the Mississippi Valley Region. — 

This includes two important areas, viz., the Upper Missis- 
sippi Valley and the Ozark Region. 

Upper Mississippi Valley Area (36,8,9). — This area em- 
braces southwestern Wisconsin, eastern Iowa, and north- 
western Illinois, but the first-named state contains the 
most productive territory. The section in the Wisconsin 
area, which may be taken as typical, involves the following 
formations, beginning at the top : — 

Niagara limestone Silurian. 

Cincinnati (Maquoketa) shales 

Galena limestone 250 ft. 

Trenton limestone .... 40-100 ft. 
St. Peter's sandstone .... 150 ft. 
Lower magnesian limestone, 100-250 ft. 
Potsdam sandstone . . . 700-800 ft. [ 



Ordovician. 



312 



ECONOMIC GEOLOGY OF THE UNITED STATES 



A ^bituminous shaly layer, knowu as the oil roek, occurs 
at the base of the Galena, and below it, or at the top of 
the Trenton, is a fine-grained limestone called the glass rock. 
Win e the series as a whole shows a very gentle southwest 
clip, there are a few low folds. 

The ore-bearing minerals, consisting of galena, smith- 
somte, and sphalerite, associated with marcasite and some 




OIL ROCK 



f T - L -J GALENA 
t±=Ezl LIMESTONE' 



>-i'-imtonj|>it : 

calcite, occur as disseminations, as honeycomb masses in 

brecciated or porous limestone, and in crevices. The last 

type, winch forms the most important source of the ore 

consists of a vertical fissure, which at its lower end splits 

into two horizontal branches called flats, while these in 
turn p a SS into a steeply dipping ^^ ^^ 

(Pigs. 42 and 65). There are at times several flats. Galena 
commonly predominates in the crevices, while sphalerite 
occurs in great abundance lower down. The main crevices 
extend approximately east and west, but there are other 



LEAD AND ZINC 313 

less important intersecting fissures. -The Galena limestone 
is the most important ore-bearing formation, but ore is 
also known to occur in the lower-lying limestones and 
sandstones, although no deposits have been worked in 
them. In the crevices the order of deposition is mar- 
casite, sphalerite, and galena. The ores, are frequently 
oxidized, yielding smithsonite and some calamine. 

A careful study of the origin of the ore bodies indicates 
that the metallic minerals have been gathered by circulat- 
ing meteoric waters from the Galena limestone ; these waters 
entered the limestone probably from the northeast, where 
the overlying shales had been eroded, and moved to the 
southwest. The ore was precipitated in crevices as sul- 
phides, either because of a reducing action exerted by bitu- 
minous matter present in the rocks or hydrogen sulphide. 

Surface waters descending crevices have produced a sec- 
ondary concentration, which has resulted in a separation 
of the zinc and galena, accompanied by a transferal of 
much of the former to lower levels. 

Lead was discovered in the Upper Mississippi area as early as 1692, 
and the first mining was done in Dubuque in 1788. The early work 
was restricted to lead mining entirely, the zinc ores being disregarded. 
Owing to uncertainty regarding the size of the deposits, the mining for 
many years has been done in a most primitive manner, but more re- 
cently prospecting at lower levels and the discovery of new ore bodies 
has stimulated the erection of better plants. Mechanical concentration 
methods have also been introduced, and while the galena can be sepa- 
rated quite thoroughly from the sphalerite and marcasite, the last two 
are parted with difficulty. On account of the presence of marcasite 
in most of the mines, the zinc ores of this district command- a lower 
price than those from other areas. For this same reason much of the 
ore cannot be used for spelter, but is employed for zinc oxide and sul- 
phuric acid manufacture. 



314 



ECONOMIC GEOLOGY OF THE UNITED STATES 



St.Louis 



Ozark Region (12,13,15,17). — The position of the region 
is shown on the map, Fig. 66. The southern part of the 
area is underlain by Carboniferous sandstone and shales, 

while the northern 
part, forming the 
Ozark plateau, and 
containing the lead 
and zinc deposits, 
is underlain by 
slightly disturbed 
sedimentaries. In 
the eastern part of 
the plateau, or Salem 
Upland, they are 
Cambro-Silurian dol- 




Fig. 66. — Map of Ozark region. After Branner, Omites and magne- 
JEng. and 31 in. Jour., LXXIII: 475. • v ± \ -i 

J sian limestone, while 

those of the western portion, or Springfield Upland, are 
Lower Carboniferous limestones. 

Within this region the following four districts are 
recognized : — 

1. Southeastern Missouri, yielding lead from dissem- 
inated ores. This area has been mentioned under Lead 
Alone. 

2. Southwestern Missouri, or the Missouri-Kansas dis- 
trict, with Joplin as the most important mining town. It 
yields chiefly zinc, with some lead. The ore occurs in 
limestones of Subcarboniferous age, filling fissures, as a 
cement of brecciated patches, or more rarely parallel to 
the bedding. The ore bodies are sometimes hundreds of 
feet in diameter. In some cases the ore extends to the 



LEAD AND ZINC 



315 



surface, and is then usually surrounded by more or less 
residual clay. 

3. Central Missouri district, containing small deposits 
of both lead and zinc. In this area the ore as far as 
exploited occurs 
rather in vertical 
crevices or chim- 
neys than in brec- 
cias. 

4. The northern 
Arkansas district, 
but partly devel- 




S 



m 



CAMBRO-SILURIAN DEVONO- LOWER UPPER 

LIMESTONE CARBONIFEROUS CARBONIFEROUS CARBONIFEROUS 
SHALE LIMESTONE SHALES 



opecl, and with 
many rich ores, oc- 

1 r\A A ^ IC " ^' — Generalized section showing occurrence of 
CUrnng as Decided lead and zinc ore iu southwest Missouri. After 

deposits (dissem- Bam - 

inations), veins (in faults or filling breccias), or as altera- 
tions. 

The common ores are sphalerite and galena, with a gangue 
of secondary chert, dolomite, calcite, and barite. Residual 
clays occur in some mines, and bitumen is not uncommonly 
found with the ores. 

These deposits afford an interesting example of the para- 
genesis of minerals, the succession seeming to be (Win- 
slow, Trans. Am. Inst. Min. Engrs., p. 651, 1893) dolomite, 
blende, galena, barite, calcite, and pyrite. 

The ores of this region are mechanically concentrated 
after mining, and the composition of an average sample of 
3800 carloads of blende shipped from the Joplin district 
in the first part of 1901 is given by Ingalls as : Zn, 58.26 ; 
Cd, .301; Pb, .70; Fe, 2.23; Mn, .01; Cu, .019; CaC0 3 , 



316 



ECONOMIC GEOLOGY OF THE UNITED STATES 



1.88; MgC0 3 , .85; Si0 2 , 3.95; BaS0 4 , .82; S, 30.72; total, 
99.773. 

Origin of the Ores. — Most of the theories of the origin 
of these ores agree in considering that their concentration 
has been caused by circulating meteoric waters which have 
collected the ore particles from the limestones, although 
in one instance at least they seem to be associated with 




Fig. 68. —A typical hoisting outfit in. the southwestern Missouri zinc region. 
Photo, bij H. F. Bain. 

igneous intrusions (19). Analyses of the limestones show 
amounts of from .001 to .015 per cent of lead and zinc in the 
Cambro-Silurian magnesian limestones and Archaean rocks 
to the southeast of the region, and from .002 to .003 per 
cent in the Lower Carboniferous limestones. These aver- 
ages calculated give 87 pounds of galena per acre in a 
one-foot layer, and 261 pounds of blende in the same 
volume of rock. W. P. Jenney, who studied the deposits 
in some detail, has emphasized the importance of ascend- 



LEAD AXD ZIXC 317 

ing waters, while Winslow has argued for their concen- 
tration by descending currents. 

The more recent studies of H. F. Bain indicate that both 
ascending and descending waters were active, and that the 
chemical reactions involved were characteristic of dilute 
solutions; rich ores, therefore, indicate great aqueous 
activity. 

The more important circulations have occurred in the 
Cambro-Silurian limestones and those of the Mississippi 
or Lower Carboniferous series, but the concentration pro- 
cess has been often repeated in many different horizons 
and at different depths. 

The chemical changes which took place in the primary 
concentration of the ores were the oxidation of sulphides 
to sulphates, the transportation of these in solution, and 
their reprecipitation as sulphides in favorable localities. 
The localization of the ore bodies has been due to the pres- 
ence of fissures which permitted the mixing of the ore-bear- 
ing solutions, but the circulation of the latter has been 
limited in many instances by impervious beds of shale, and 
organic matter has served as a reducing agent. All of the 
ores are found to be closely associated with lines of sub- 
terranean seepage, and since the open character of the brec- 
cias favored circulation, much ore is found in them. Where 
folding has occurred, the water has also sought the troughs 
of synclines as in the Lake Superior district. 

In the section presented in the Ozark region, the Devono- 
Carboniferous shales and the undifferentiated Carboniferous 
shales afforded impermeable barriers to circulation. The 
former, where not faulted, held down the ascending solu- 
tions; but where absent or fissured, the solutions from the 



318 ECONOMIC GEOLOGY OF THE UNITED STATES 

underlying Cambro-Silurian formation were able to pass up- 
ward into the Mississippian and impregnate them. 

The Cambro-Silurian ores were first concentrated by deep 
circulation, and formed the disseminated ores. Later, when 
erosion cut away the Devono-Carboniferous capping, further 
concentration took place by descending solutions, giving rise 
to the ore bodies in crevices, breccias, and synclines. 

Two concentrations have occurred in the Mississippian 
limestones. 

The ore bodies are of two types, viz. : (1) those containing 
sulphides and clean untarnished minerals, the result of pri- 
mary concentration ; and (2) those due to surface concen- 
tration, and containing oxidized ones with red clay. The 
ores pass into sulphides below the water level. 

Where ascending solutions alone acted, the ore bodies are 
less rich but more reliable, however secondary enrichment of 
the deposits has been marked. 

Rocky Mountain States (28) . — Although much ore is 
mined in this region, its resources of this metal are still 
largely undeveloped, and up to 1903 most of the ore mined 
was either shipped to Kansas smelters or exported. The 
recent construction of a zinc-smelting plant at Pueblo, 
Colorado, and the enlargement of the oxide plant at 
Canyon, Colorado, has largely stimulated the production 
of both that state and Utah. 

The zinc-producing localities of Colorado are chiefly the 
same as those yielding lead, Leadville being the largest pro- 
ducer. According to Ingalls the zinc shipments average 
about 25 per cent Zn, 10 Pb, 2.2 Fe, 4 Si0 2 , 39 S, and 10 
oz. Ag. Much zinc ore is also supplied by the mines at 



LEAD AXD Zi:N T C 319 

Creede (Ingalls), where it is concentrated to a product 
assaying 55-59 per cent Zn, 3.75-6 Pb, and 1.1-2.1 Fe, 
which is shipped to Kansas. The blende carries 2-3 oz. 
Ag per T. Blende concentrates are also produced at Mon- 
tezuma and Rico, Colorado. The Colorado ores are usually 
of lower grade than the Joplin ones, and their complex 
nature makes treatment difficult ; indeed until recently zinc 
has been a source of loss to the miners and smelters, those 
ores high in zinc being either neglected or thrown out. 

In addition to Colorado, New Mexico produces considerable 
ore, the deposits near Hanover yielding blende and smith- 
sonite (28) from Carboniferous limestone near igneous con- 
tacts. It was shipped to Wisconsin for treatment. Utah, 
Idaho, and Montana will no doubt also become important 
sources of supply in the future. 

Uses of Lead and Zinc. — Both of these are important base 
metals, although in value of production they rank below gold, 
silver, copper, and iron, neither do they come into competi- 
tion with these, for they lack the high tenacity of iron and 
steel, the conductivity of copper, and the value resulting from 
scarcity possessed by gold and silver. They are of value, 
however, on account of their high malleability and the 
application of their compounds for pigments. 

Uses of Lead. — Lead finds numerous uses in the arts, the 
most important being for white lead. Litharge, the oxide 
of lead, is used not only for paint, but also somewhat in the 
manufacture of glass, although red lead is more frequently 
employed instead. 

A further use of lead is for making pipe for water supply, 
sheet lead for acid chambers, and shot. 



320 ECONOMIC GEOLOGY OF THE UNITED STATES 

Among the alloys formed by lead are type metal (lead, anti- 
mony, and bismuth, with copper or iron), white metal, organ 
pipe composition, and fusible alloys used in electric lighting. 

In addition to these, the acetate, carbonate, and other com- 
pounds are used in medicine. In smelting, lead is used to 
collect the gold and silver, and the bulk of the lead of com- 
merce is obtained as a by-product in the smelting of the 
precious metals. 

Uses of Zinc. — Metallic zinc is used for a variety of 
purposes, partly owing to its slight alteration in air, and 
secondly, because it can be rolled into thin sheets. In this 
condition it is used extensively for roofing and also for plumb- 
ing, and as a coating to iron this metal is extensively called 
for in galvanizing. 

One of the most important applications is for making 
brass, which is ordinarily composed of from 6Q to 83 parts 
of copper and 27 to 34 parts of zinc. The composition 
varies, entirely depending on the use to which it is to be put, 
and, with the variation in proportion, the color becomes more 
golden, or whiter, according as the percentage of copper 
is increased or decreased. With an increase in the amount 
of zinc, the alloy becomes more fusible, harder, and 
more brittle. Brass was made long before zinc, as a metal, 
was discovered, and Aristotle says that the people by the 
Euxine Sea made their copper a beautiful whitish color by 
mixing it with a white earth found there. Strabo also tells 
us that the Phrygians made brass in this way. 

White metal is an alloy of zinc and copper in which zinc 
predominates, and which is often employed for making 
buttons. Imitation gold is also made by alloying zinc 
with a predominance of copper, varying from 77 to 85 per 



LEAD AND ZINC 



321 



cent of the mass, and this is in common use as " gold foil " 
for gilding. Zinc is also made use of in the construction of 
electric batteries. 

German silver has 60 parts copper, 20 zinc, and 20 nickel. 
Its use is for mathematical and scientific instruments. 

Production of Lead and Zinc. — The production of lead in 
the United States from 1825 to 1900 was as follows : — 



Year 


Short Tons 


Year 


Short Tons 


1825 

1835 

1845 

1855 

1865 


1,500 
13,000 
30,000 
15,800 
14,700 


1875 

1885 

1895 

1900 


59,640 
129,412 
170,000 
270,824 



About 70 per cent of the lead produced in the United 
States is derived from five districts, viz. : Southeastern Mis- 
souri; Joplin, Missouri; Leadville, Colorado: Park City, 
Utah ; and Coeur d'Alene, Idaho. 

Lead Content of Ores smelted in the United States 
from 1901 to 1903 





1901 


1902 


1903 


Colorado 

Idaho 

Utah 

Montana 

New Mexico 

Nevada 

Arizona 

California 

Washington 1 

Oregon, Alaska, South Dakota, V 
Texas J 

Missouri, Kansas, Wisconsin, 
Illinois, Iowa, Virginia, 
Kentucky 


Short tons 

73,265 

79,654 

49,870 

5,791 

1,124 

1,873 

4,045 

381 

1,029 
67,172 


Short tons 

51,833 

84,742 

53,914 

4,438 

741 

1,269 

599 

175 

f 1,457 

\ 

{ 2,184 

79,445 


Short tons 

45,554 

99,590 

51,129 

3,303 

613 

2,237 

1,493 

55 

538 

1,765 
86,597 


Total 


284,204 


280,797 


292,874 



322 



ECONOMIC GEOLOGY OF THE UNITED STATES 



The production of spelter in the United States from 1873 
to 1900 was : — 



Year 


Short Tons 


Year 


Short Tons 


1873 

1880 

1885 


7,343 
23,239 

40,688 


1890 

1895 

1900 


63,683 

89,686 

123,886 



Production of Spelter from 1901 to 1903 by States 



1901 
1902 
1903 



Eastern 

AND 

Southern 
States 



Short tons 

8,603 
12,180 
12,301 



Illinois 

AND 

Indiana 



Short tons 

44,896 
47,096 
47,659 



Kansas 



Short tons 

74,240 
86,564 

88,388 



Missouri 



Short tons 

13,083 
11,087 

9,994 



Colorado 



Short tons 



877 



Total 



Short tons 

140,822 i 
156,927 2 
159,219 3 



World's Production of Lead. — This in 1902 amounted to 
926,895 metric tons. Of this quantity the United States 
produced approximately 26 per cent ; Spain, 19 per cent ; 
Germany, 15 per cent ; and Mexico, 11 per cent. Of these 
countries Spain and Mexico afforded the greatest surplus 
production, and both Germany and the United Kingdom 
required more lead than they mined. 

The figures of world's production together with imports 
and exports in metric tons for 1902 are given below : — 



1 Including 2716 tons dross spelter. 

2 Including 2675 tons dross spelter. 

3 Including 3302 tons dross spelter. 



LEAD AND ZINC 



323 





Produc- 








Consump- 




tion 


Imports 


Total 


Exports 


tion 


Austria-Hungary . . 


13,543 


8,706 


22,249 


53 


22,196 


Belgium . . . 






19,500 


53,000 


72,500 


50,000 


22,500 


France .... 






18,817 


72,730 


91,547 


6,454 


85,093 


Germany . . . 






140,331 


39,006 


179,337 


23,100 


156,237 


Italy .... 






26,494 


7,563 


34,057 


5,650 


28,407 


Prussia . . . 






250 


23,000 


23,250 




23,250 


Spain .... 






177,560 




177,560 


172,480 


5,080 


United Kingdom 






27,100 


235,522 


262,622 


24,408 


238,214 


United States . 






342,160 


65,235 


407,395 


129,637 


277,758 



World's Production of Zinc. — The production of zinc ore 
and spelter in metric tons for 1902 is given below : — 



Country 


Spelter 


Ore 


Country 


Spelter 


Ore 


Germany . . . 


174,927 


702,504 


Austria . . . 


7,960 


31,927 


United States . 


143,552 


500,000 


Spain 








5,569 


127,618 


Belgium . . . 


124,780 


3,852 


Italy . 








485 


149,965 


United Kingdom 


40,244 


25,462 


Sweden 










48,783 


France .... 


36,282 


57,982 


Algeria 










33,139 


Holland . . . 


20,760 




Greece 










18,020 


Russia .... 


8,280 




Tunis 










18,400 



The above table indicates that the mining districts and 
smelting centers are not identical. Belgium and Holland 
have a smelting industry greatly in excess of the local min- 
ing interests, but in the United States they are in approxi- 
mate equilibrium. 



REFERENCES ON LEAD AND ZINC 

Arkansas: 1. Adams, U. S. Geol. Surv., Bull. 213 : 187, 1904. (N. Ark.) 
2. Adams, U. S. Geol. Snrv., Prof. Paper No. 24, 1904. 3. Branner, 
Ark. Geol. Surv., Rept. for 1892. (N. Ark.) —Colorado : 4. Em- 
mons, U. S. Geol. Surv., Mon. XII, 1886. (Leadville.) 5. Ran- 
some, U. S. Geol. Surv., 22d Ann. Rept, II : 229, 1902. (Rico Mts.) 



324 ECONOMIC GEOLOGY OF THE UNITED STATES 

6. Spurr, U. S. Geol. Surv., Mon. XXXI, 1898. (Aspen.) — Idaho : 

7. Lindgren, U. S. Geol. Surv., 20th Ann. Rept., Ill: 190, 1900. 
(Wood River district.) — Illinois : 8. Bain, U. S. Geol. Surv., Bull. 
225: 202, 1904, and Bull. 246, 1904. — Iowa: 9. Leonard, la. Geol. 
Surv., VI : 10, 1897. — Kentucky : 10. Ulrich and Smith, U. S. Geol. 
Surv., Prof. Paper No. 36, 1905. — Massachusetts : 11. Hubbard, 
Amer. Jour. Sci., IX: 167, 1825. — Missouri : 12. Bain, U. S. Geol. 
Surv., 22d Ann. Rept., II: 23, 1901. (Ozark region.) 13. Bain, 
U. S. Geol. Surv., Bull. 267, 1905. (Mo.) 14. Ball and Smith, Mo. 
Bureau Geol. and Mines, Bull. Vol. I, 2d Series, 1903. (Central 
Mo.) 15. Branner, Eng. and Min. Jour., L XXIII : 475, 1902. 
(Ozark region.) 16. Jenney, Amer. Inst. Min. Engrs., Trans. XXII : 
189, 1904. (Mo.) 17. Winslow, Mo. Geol. Surv., Vols. VI and VII, 
1894. 18. Winslow, U. S. Geol. Surv., Bull. 132, 1896. (S. E. 
Mo.) 19. Wheeler, Eng. and Min. Jour., LXXVII: 517, 1904. 
(Relation of lead ore to igneous rock.) — New Jersey: 20. Kemp, 
Trans. N. Y. Acad. Sci., XIII: 76, 1894. 21. Wolff, U. S. Geol. 
Surv., Bull. 213 : 214, 1903. 22. Bason, Amer. Inst. Min. Engrs., 
Trans. XXIV: 121, 1894. A U. S. Geol. Surv. report by Spencer 
is also in preparation. — New Mexico: 23. Blake, Amer. Inst. 
Min. Engrs., Trans. XXIV: 187, 1894. (S. W. New Mexico.) 
24. Keyes, Min. Mag., XI, Aug., 1905. (Magdalena Mts.) — New 
York: 25. Ihlseng, Eng. and Min. Jour., LXXV: 630, 1903. (El- 
lenville.) — Pennsylvania: 25a. Clerc, U. S. Geol. Surv., Min. Res. 
1882, 361. — Tennessee : 26. Keith, U. S. Geol. Surv., Bull. 225 : 208, 
1904. 27. See also Morristown, Maynardville, and Cleveland folios, 
U. S. Geol. Surv. — United States: 28. Bain, U. S. Geol. Surv., Bull. 
260 : 251, 1905. 29. Whitney, Metallic Wealth of U. S., 1854. (Ap- 
palachians.) — Utah: 30. Emmons, Amer. Inst. Min. Engrs., Trans. 
XXXI: 675, 1901. (Delamar and Hornsilver Mines.) 31. Tower 
and Smith, U. S. Geol. Surv., 19th Ann. Rept., Ill: 601, 1899. 
(Tintic.) — Virginia: 32. Boyd, Resources of Southwest Virginia, 
1881. 33. Case, Amer. Inst. Min. Engrs., Trans. XXII : 511, 1894. 
34. Payne, Eng. and Min. Jour., LXXVIII : 544, 1904. 35. Watson, 
Va. Geol. Surv., Bull. 1, 1905. (Va.-Tenn.) — Wisconsin : 36. Grant, 
Wis. Geol. and Nat. Hist. Surv., Bull. 9, 1903. 



CHAPTER XVII 



GOLD AND SILVER 



Gold and silver are obtained from a variety of ores, in 
some of which the gold predominates, in others silver, while 
in still a third class these two metals may be mixed with the 
baser metals, lead, copper, and zinc. Few gold ores are 
absolutely free from silver, and vice versa, so that a separate 
treatment of the two is more or less difficult ; however some 
lead-silver ores, although they may carry some gold, are 
sufficiently prominent to be discussed as a separate type, and 
are described as such on a later page. 

Ores of Gold. — Gold occurs in nature chiefly as native 
gold, mechanically mixed with pyrite, or as a telluride such 
as calaverite (Au, 39.5 per cent; Ag, 3.1 per cent; Te, 57.4 
per cent). 1 

Ores of Silver. — The minerals which may serve as ores 
of silver, together with the percentage of silver they con- 
tain, are : — 



Ores 

Native silver 

Argentite, silver glance 

Pyrargyrite, ruby silver 

Proustite, light ruby silver .... 
Stephanite, brittle silver, black silver 

Cerargyrite, horn silver 

Bromyrite 

Embolite 

Polybasite 



Ag 

(Ag 2 S) 

3 Ag 2 S, Sb 2 S 3 

3 Ag'S, AsgSg 

5 Ag,S, Sb 2 S 3 

AgCl 

AgBr 

Ag(ClBr) 

9Ag,S,Sb,S 3 



Ag 



100.00 
87.1 
59.9 
65.5 
68.5 
75.3 
57.4 
64.5 
75.6 



12.9 
17.8 
19.4 
16.3 



approx. 



1 Other tellurides are sylvanite, kalgoorlite, and krennerite. 
325 



326 ECONOMIC GEOLOGY OF THE UNITED STATES 

Mode of Occurrence. — Most of the gold and silver mined 
in the United States is obtained from fissure veins, or closely 
related deposits of irregular shape (79), in which the gold 
and silver ores have been deposited from solution, either in 
fissures, or other cavities, or by replacement. Considerable 
gold and a little silver is obtained from gravel deposits. 
Some true contact deposits are known. Gold has been found 
to occur in rare instances as an original constituent of igneous 
rocks (1, 8, 11) and also metamorphic ones (12), but there are no 
known deposits of commercial value belonging to this type. 

The gold and silver-bearing fissure veins include two 
prominent types (79), viz. : (1) the quartz veins, and (2) the 
propylitic type, in which the metasomatic alteration of the 
wall rock is often propylitic, that is, accompanied by the for- 
mation of chlorite and epidote, but near the veins of sericite 
and kaolin. In the quartz-vein type silver is present usu- 
ally in but small quantities, while in the propylitic type the 
silver often is an important constituent." 

While the mode of occurrence of gold and silver is quite 
variable, the character of the wall rock is equally so, gold 
and silver ores being found in either sedimentary or igneous 
rocks, and along the contact between the two, showing that 
the kind of rock exerts little influence, except perhaps where 
replacement has been active. On the other hand the influ- 
ence of locality is much stronger, for it has been found that 
many gold and silver-bearing deposits are closely associated 
with masses of igneous rock, the most common of these being 
diorite, monzonite, quartz-monzonite, granodiorite, while true 
granites are rare as associates. A second large class of vein 
systems shows a close association with lavas of recent age, 
and the telluride ores rather favor these (6). 



GOLD AND SILVER 327 

Weathering and Secondary Enrichment. — The superficial 
alteration of gold ores differs somewhat from that of deposits 
containing ores of the other metals. In quartz veins with 
auriferous pyrite, the change of the latter to limonite leaves 
a rusty quartz with nuggets or threads of free gold, and 
leaching may remove most of the iron. Some of the gold 
may also be leached out by the ferric sulphate, formed by 
the oxidation of the pyrite, and carried to lower levels, where 
it is reprecipitated. Whether the reprecipitation of the gold 
is due to pyrite or carbonaceous matter, is, in some cases at 
least, an unsettled question (4, and Ref. on ore deposits). 

The silver sulphides are changed to sulphates or chlorides, 
part of which at least are leached out of the gossan and 
carried to lower levels, where they are reprecipitated by iron 
or even copper sulphides. 

Classification. — The gold and silver ores are some- 
times grouped (80) according to their associations, as below ; 
this also has the advantage of bringing out more clearly 
their metallurgical character. 

1. Placers or gravel deposits. These serve chiefly as a 
source of native gold, but may and often do contain a little 
silver, much of which is never separated from the ore in 
which it occurs. These gravels are derived chiefly from 
quartz veins of Mesozoic age in the Pacific coast region, 
and to a less extent from pre-Cambrian veins of the Ap- 
palachian region and Black Hills of South Dakota. Some 
are also derived from veins in Tertiary lavas, but these 
usually contain the metals in such a finely divided con- 
dition, or in such combination, that they do not readily 
accumulate in stream channels. 



328 ECONOMIC GEOLOGY OF THE UNITED STATES 

2. Quartzose or dry ores, in which the gold and some silver 
are found in a quartz gangue, and are either free or mixed 
with sulphides, commonly pyrite. They are of varying age. 
Those of California, Oregon, and Alaska are Mesozoic and 
associated chiefly with quartz monzonite, granodiorite, and 
diorite. Another great class of post-Miocene age, found 
chiefly in Colorado, Nevada, and Montana, is associated with 
Tertiary lavas and characterized by bonanzas. The most 
productive ones carry fluorite and normally also tellurides. 
In some, gold may predominate ; in others, silver. A third 
class, of pre-Cambrian age, is found in the Atlantic States, 
Wyoming and South Dakota, the last mentioned including 
the famous Homestake Mine. These are classified as dry 
ores, because they are not as a rule smelting ones ; they con- 
tain limited quantities of copper and lead, but may have 
some pyrite. 

3. Gold and silver bearing copper ores. These are widely 
distributed throughout the United States, and exhibit great 
differences in form and age, neither do all the occurrences 
yield much gold or silver. The output is obtained chiefly 
from Colorado, Utah, and Montana. Those of the last two 
states, which supply most of the production, are found as 
replacement veins in granites or early Tertiary igneous rocks. 
The large copper deposits of Arizona produce but little gold 
or silver, with the exception of those at Jerome. This class 
of ores yields about one third of all the silver mined in 
the United States. 

4. Gold and silver bearing lead ores. This class includes 
a variety of deposits, containing much lead, and also silver, 
with gold usually in subordinate amounts. They occur 
chiefly in Colorado, Utah, and Idaho, and furnish about one 



GOLD AND SILVER 329 

half of the silver obtained in the United States. They are 
discussed separately under the head of Silver-Lead ores. 

A subtype of this class is represented by the veins of 
argentiferous galena and tetrahedrite of the Wood River 
district, Idaho. These are veins in slates near the contact 
of intrusive granite and are of late Mesozoic age. Arizona, 
California, Washington, and New Mexico produce small 
amounts of argentiferous lead ores. 

Geological Distribution. — Gold and silver ores have been 
formed at a number of different periods in the geological 
history of the continent, notably in the pre-Cambrian, Cam- 
brian, Cretaceous, and Tertiary ages, but Silurian, Devonian, 
and Carboniferous gold deposits are not definitely known to 
exist in North America, although some of the Appalachian 
veins may be of this age (79). Silver ores show much the 
same geological distribution. 

Extraction. — Since gold and silver ores vary so in their 
mineralogical associations and richness, the metallurgical 
processes involved in their extraction are varied and often 
complex. 

Those ores whose precious metal contents can be readily 
extracted after crushing, by amalgamation with quicksilver, 
are termed free-milling ores. This includes the ores which 
carry native gold or silver, and often represent the oxidized 
portions of ore bodies. Others, containing the gold as tel- 
luride or containing sulphides of these metals, are known as 
refractory ores and require more complex treatment. These, 
after mining, are sent direct to the smelter if sufficiently 
rich, but if not they are often crushed and mechanically 
concentrated. The smelting process is also used for mixed 



330 ECONOMIC GEOLOGY OF THE UNITED STATES 

ores, the latter being often smelted primarily for their lead 
or copper contents, from which the gold or silver is then 
separated. While in some cases there are smelters at the 
mines, still there is a growing tendency towards the central- 
ization of the industry, and large smelters are now located 
at Denver, Salt Lake City, etc., which draw their ore supply 
from many mining districts. 

Low-grade ores may first be roasted, and the gold then 
extracted by leaching with cyanide or chlorine solutions. 
The introduction of the cyanide and chlorination processes, 
which are applied chiefly to gold ores, has permitted the 
working of many deposits formerly looked upon as worth- 
less, and in some regions even the mine dumps are now 
being worked over for their gold contents. It is estimated 
that in 1902 $8,000,000 worth of gold ores were cyanided. 
The chief fields are in the Cripple Creek region of Colo- 
rado ; the De Lamar district, Idaho ; Marysville, Montana ; 
Bodie, California ; and in Arizona. 

The most important gold-milling centers of the United 
States are the Mother Lode district of California, the Black 
Hills, South Dakota, and Douglas Island, Alaska. 

The value of ore and bullion is determined from a sample 
assay, and the smelter, in paying the miner for his ore, 
allows for gold in excess of $ 1 per ton of ore at the coin- 
ing rate of $20.67 per ounce, and for silver at New York 
market price, deducting 5 per cent in each case for smelter 
losses. Lead and copper are paid for in the same manner, 
as are also iron and manganese, if there is a sufficient quan- 
tity present. No allowance is, however, made for zinc, 
and, in fact, a deduction is made if it exceeds a certain 
per cent. 



GOLD AND SILVER 



331 



Distribution of Gold and Silver Ores. — Gold ores are 
widely distributed in the Cordilleran region and Appa- 
lachian province, while the silver ores are found chiefly 
between the Great Plains and Pacific coast ranges, exclu- 
sive of the Colorado plateau region. This occurrence in 
two widely separated areas is brought out in an interest- 
ing manner in Fig. 69. 




Fig. 69. — Map showing distribution of gold and silver ores in United States. 
Adapted from Eansome, Min. Mag., X: 1. 

More than a third of the United States production of 
gold comes from the southern half of the Rocky Moun- 
tains, Colorado being the main producer. In this area, 
however, the ores vary widely in their mineralogical asso- 
ciations, the gold occurring mostly in combination with 
silver, lead, copper, and zinc ores, but also at times free, 
or, in the most productive district, as a telluride. 

The Pacific belt, excluding Alaska, supplies about one 
fourth the total amount of gold produced, the famous 
Mother Lode region, mentioned later, being the most im- 



332 ECONOMIC GEOLOGY OF THE UNITED STATES 

portant producer. Alaska yields about 10 per cent, and 
the Basin Range province about 14 per cent, collected 
from widely separated deposits in Utah, Nevada, Arizona, 
and New Mexico, and in which the gold is associated with 
copper, silver, or lead. 

Probably two thirds of the silver obtained in the United 
States comes from the Rocky Mountain region, Colorado 
alone yielding about one third, while Montana supplies 
about one third of the total amount produced, and about 
three fourths of this is obtained as a by-product in copper 
smelting. The Basin Range province furnishes about 28 
per cent, two thirds of this coming from Utah, especially 
from the Park City mines near Salt Lake City (83). 

The gold and silver occurrences of the United States 
and Alaska can be grouped under five areas, as follows : ■ — 

1. Cordilleran region. 

2. Black Hills, South Dakota region. 

3. Michigan region. 

4. The eastern crystalline belt. 

5. Alaska. 

Of these, the first, second, and fifth are the most impor- 
tant, while the third is insignificant. 

CORDILLERAN REGION 

This area contains a number of important deposits of gold 
and silver ores, occurring chiefly in quartz veins, and to a 
lesser extent in gravels. There are also some representa- 
tives of the propylitic type. 

Pacific Coast Cretaceous Gold-quartz Ores. — Extending 
along the Pacific coast from Lower California up to the 







Plate XX 


f~ •'» fir- - '' 
E :r - 






^ ; 




„•"- 



Fig. 1. — Kennedy mine on the Mother Lode near Jackson, Calif. 




Fig. 2. — Auriferous quartz veins in Maryland mine, Nevada City, Calif. After 
Lindgren, U. S. Geol. Surv., Ylth Ann. Rept., III. 



GOLD AND SILVER 333 

British Columbia boundary there is a gold belt of great 
importance, which throughout its extent is characterized 
by quartzose ores and gold-bearing sulphides. The de- 
posits belonging to this are especially important in Cali- 
fornia, but farther north, in Oregon and Idaho, the veins 
in many cases have been covered up by the lava flows 
of the Cascade Range, and those known in that region 
differ somewhat from the California deposits in containing 
many mixed silver-gold ores and also veins carrying aurif- 
erous sulphides without free gold. The ores of this belt 
are all of undoubted Mesozoic age, and are accompanied 
by many extensive placer deposits, which have been derived 
by the weathering down of the upper parts of the quartz 
veins, the portions now remaining in the ground repre- 
senting probably but the stump of originally extensive 
fissure veins (79). 

Among the deposits of this belt two groups stand out 
in some prominence, namely, those of the so-called Mother 
Lode district and of Nevada County. 

Mother Lode Belt (25, 27). — This includes a great series of 
quartz veins, beginning in Mariposa County and extending 
northward for a distance of 112 miles. The veins of this 
system break through black, steeply dipping slates and 
altered volcanic rocks of Carboniferous and Jurassic age, and 
since they are often found at a considerable distance from 
the granitic rocks of the Sierra Nevada, they have apparently 
no genetic relation with them. The veins, which occur either 
in the slate itself or at its contact with diabase dikes, show a 
remarkable extent and uniformity, due to the fact that in 
the tilted layers of the slates there lay planes of weakness 
for the mineral-bearing solution to follow. The ore is native 



334 



ECONOMIC GEOLOGY OF THE UNITED STATES 



gold or auriferous pyrite in a gangue of quartz, and the 
average value may be said to vary from $3 or $4 up to $50 
or |60 per ton. The veins often split and some of the mines 
have reached a depth of several thousand feet. 





Hat , Ng 



Fig. 70. —Map and section of portion of Mother Lode district, Calif. Pgv, river 
gravels, usually auriferous; Ng, auriferous river gravels. Sedimentary 
rocks: Jm, mariposa formation (clay, slate, sandstone, and conglomerate); 
Cc, calaveras formation (slaty mica schists). Igneous rocks: If I, latite; 
Nat, andesite tuffs, breccia, and conglomerate; mdi, meta-diorite ; Sp, ser- 
pentine; ma, meta-andesite ; ams, amphibole schist. From U. S. Geol. 
Surv., Atlas Folio, Mother Lode sheet. 

Nevada County (26). — In Nevada County the mines of 
Grass Valley and Nevada City are likewise quartz veins, but 
they occur along the contact between a granodiorite and 
diabase porphyry, as well as cutting across the igneous rock 
(Fig. 71). Two systems of fault fissures occur, and in 
these the ore is fouud either in native form or associated 



GOLD AND SILVER 



335 



with metallic sulphides. The width of the vein averages 
from 2 to 3 feet, and the lode ore generally occurs in well- 
defined bodies or pay shutes. The vein filling was deposited 
by hot solution, and while the wall rocks contain the rare 
metals in a disseminated condition, Lindgren (2G) believes 
that the ores have been leached out of the rocks at a con- 
siderable depth. The mines at Nevada City and Grass 
Valley have been large producers of gold and some silver. 
Placer mines have furnished a small portion of the product, 
but at the present day these latter are of little importance. 




I ^a I GRANODIORITE 



|V_>/| METAMORPHIC 
h^M SCHIST AND DIABASE 



a.MERRIFIELD VEIN b. URAL VEIN O.SLATEVEIN 



Fig. 71. — Section illustrating relations of auriferous quartz veins at Nevada City, 
Calif. After Lindgren, U. S. Geol. Surv., Ylth Ann. Rept., II. 

In Oregon, the quartz veins are worked in Baker County, 
which is the most important gold-producing region of the 
state (72,73). Gold ores with sulphides in quartz gangue 
are worked in the Monte Cristo district of Washington (88). 

Central Belt of Gold-Silver Ores. — To the east of the Creta- 
ceous gold-quartz belt there lies a second one, in the central 
and eastern part of the Cordilleran region, containing many 
gold and silver deposits of late Cretaceous or early Ter- 
tiary age, although they occur in older rocks, such as Car- 
boniferous. 



336 



ECONOMIC GEOLOGY OF THE UNITED STATES 



Mercur, Utah. — The gold-silver mines of the Mercur (85) 
district in Utah form perhaps the most important occurrence 
in this central zone. Here the Carboniferous limestones, 
shales, and sandstones, representing about 12,000 feet of 
sediments, are folded into a low anticline. Near the center 
of the section is the great blue limestone, carrying an upper 
and a lower shale bed. Quartz porphyry has intruded the 
limestone, and at two places especially, spread out laterally 
in the form of sheets, on whose under side the ore is found, 
the silver ores under the lower sheet, the gold ores under the 




EAGLE HILL PORPHYRY 
GREAT BLUE LIMESTONE 



GREAT BLUE LIMESTONE 



LOWER INTERCALATED SERIES 
'. OWER LIMESTONE 



Fig. 72. —Section of Mercur, Utah. After Spurr, U. S. Geol. Surv., ldth Ann. 

Rept., II. 

upper one, about 100 feet above the first. The silver ore is 
cerargyrite and argentiferous stibnite in a silicified belt of the 
limestone. The gold is native and occurs in a belt of re- 
sidual contact clay, near northeast fissures cutting the lime- 
stone, being oxidized in places and accompanied by sulphides 
in others. The ore runs 1-19 ounces of silver per ton, and 
2-3 ounces of gold, with a gangue of quartz, barite, limonite, 
and arsenical sulphides. The silver minerals are thought to 
have been deposited by heated solutions which came up along 
the igneous sheet some time after its intrusion, and the deposi- 
tion of the gold ore is believed to have taken place some time 



GOLD AND SILVER 337 

after the silver was deposited. Some doubt exists as to the 
exact source of the ascending waters, but in all probability 
they were derived from some deep-seated cooling laccolith. 
The ores are especially suited to the cyanide treatment. 

Other Occurrences. — The northward continuation of this 
belt of gold-bearing veins in Idaho and Montana presents 
somewhat different types of deposits, for there the vein's are 
causally connected with great batholiths of Mesozoic gran- 
ite ; and while the veins resemble those of the Pacific Coast 
in the quartz filling and free gold contents, they differ from 
the latter in containing more silver, and often large quanti- 
ties of sulphides with little free gold. In fact in their geo- 
logic relations they are intermediate between the quartz vein 
and propylitic type. Of special prominence are those of 
Marysville, Montana, and Idaho Basin, Florence, etc., in 
Idaho. This difference is more marked in the Montana 
occurrences, in which the gold becomes subordinate and is 
obtained as a by-product in silver mining. 

Eastern Belt of Tertiary Gold-Silver Veins. — Of greater 
importance than the preceding class are the veins of Tertiary, 
mostly post-Miocene, age, which, according to Lindgren, are 
characteristic of regions of intense volcanic activity, and cut 
across andesite flows, or more rarely rhyolite and basalt. 
The veins may be entirely within the volcanic rocks, or the 
fissures may continue downward into the underlying rocks, 
which have been covered by the extrusive masses. Most 
of these Tertiary deposits belong to the propylitic class, 
showing characteristic alterations of the wall rock. The 
ores are commonly quartzose, and though either gold or 
silver may predominate, the quantities of the two metals are 



338 



ECONOMIC GEOLOGY OF THE UNITED STATES 



apt to be equal. Bonanzas are of common occurrence, and 
on this account the mines may be very rich but short-lived ; 
still, the workable ore in many, extends to great depths, 
but is less rich than nearer the surface. Extensive and 
rich placers are rarely found in the Tertiary belt of veins, 
for the reason that the fine distribution of the gold is 
not favorable to its concentration and retention in stream 




Fig. 73. — Map of Colorado showing location of mining regions. After Richard, 
Amer. Inst. Min. Eng., Trans., 1904. 

channels. Deposits of this type are worked in a number 
of states, including Colorado, Nevada, Arizona, New Mexico, 
and Idaho. Colorado leads in the production of gold 
ores, for in no state are the Tertiary deposits of the pro- 
pylitic type developed on such a scale. 

Cripple Creek (39, 45, 47). — This district, which is the 
most important in this belt, is a producer of ores containing 



GOLD AND SILVER 



339 



gold almost exclusively, and may therefore be mentioned 
in some detail. The region lies about ten miles west of 
Pikes Peak proper, but in the foothills of this mountain 
mass. 

The most common rock of the region is the red Archaean 
granite of Pikes Peak, in which, however, are inclusions of 
still older schists. In Tertiary 
times, the region was one of 
great volcanic activity, which 
began with the expulsion of the 
breccias of phonolitic and pos- 
sibly in part andesitic types, 
and was followed by a series of 
phonolitic rocks, which grade 
into each other. Finally, there 
were intrusions of basaltic dikes 
of several types. 

The ore is chiefly calaverite, 
and to a less extent sylvanite, 
and probably some other gold- 
silver-lead tellurides. The tel- 
lurides are often associated 
with auriferous and highly 
argentiferous tetrahedrite, molybdenite, and even stibnite. 
Pyrite, though widely disseminated in both country rock 
and fissures, rarely carries enough gold to serve as an ore. 
Native gold exists only as an oxidation product of the tel- 
luride. The common gangue minerals are quartz, fluorite, 
and dolomite ; secondary orthoclase is sometimes prom- 
inent in the granites, while other minerals occur in small 
amounts. 




ORE ALONG SHEETEOZONE- 

Fig. 74. — Section of vein at Cripple 
Creek, Colo. After Richard. 



340 ECONOMIC GEOLOGY OF THE UNITED STATES 

Two types of ore bodies exist : 1. Fissure veins, some- 
times simple, but more often compound, and formed in the 
more or less closely spaced fractures of a sheeted zone. 
These may occur in any kind of rock, but favor the brec- 
cias. Their dip is generally steep, and the lode may vary 
from 1 foot to 50 or 60 feet in width. A subtype of this 
are composite veins in sheeted basalt dikes. 

2. Irregular deposits, often of large size, formed by the 
replacement of granite, and usually occurring close to or 
within 1000 feet of its contact with the breccias. The 
ore is of somewhat lower grade than that found in the 
fissures. 

The two types are not always distinct, and in both the 
ore has been deposited in relatively small spaces, 'with but 
small quantities of gangue minerals, so that the fissures are 
never completely filled. The ores which show oxidation 
to a depth of from 200 to 400 feet often occur in shutes, 
but no evidence of secondary enrichment has been found 
by recent investigators. The principal productive zone does 
not seem to extend more than 1000 feet from the surface, 
and while ore may be looked for below this, the quantity 
of it will probably be less. 

The Cripple Creek ores as a rule run low in silver and 
from 1 to 10 ounces of gold per ton, with an average value 
of 130 to $40 per ton. Most of the ores are treated by the 
chlorination or cyanide process, especially the former, and 
about one sixth of the output is shipped directly to the 
smelters at Denver and Pueblo. 

The rapid rise of this district is well shown by the fol- 
lowing figures of production. A maximum was reached in 
1900, since which the output has gradually declined. 



Plate XXI 




Fig. 1. — View of Independence Mine and Battle Mountain, Cripple Creek, Colo. 
A. J. Harlan, photo. 




Fig. 2. — General view of region around Tonopah, Nev. •/. E. Spurr, photo. 



GOLD AND SILVER 341 

Production in Cripple Creek District in 1893-1903 



Year 


Value 


Year 


Value 


1893 

1894 . 

1895 

1896 

1897 


$2,010,367 

2,908,702 

6,879,137 

7,512,911 

10,139,708 

13,507,244 


1899 

1900 

1901 

1902 

1903 

Total .... 


$15,658,254 
18,073,539 
17,261,579 
16,912,783 
12,967,338 


1898 


8123,831.562 



San Juan Region. — As an example of a more mixed 
type of ore of this class may be mentioned the San Juan 
region of southwestern Colorado, which includes the counties 
of San Juan, Dolores, La Plata, Hinsdale, and Ouray, and is 
one of the most important gold and silver producing regions 
of the state, being noted for its persistent vertical veins, 
carrying gold, silver, and lead ores in varying proportions. 
Those in the vicinity of Rico are mentioned under Silver- 
Lead. Other important mining camps are Silverton, Creede, 
Telluride, and Ouray. 

The rocks of the San Juan district consist of a series of 
older sedirnentaries, ranging from Algonkian to Cretaceous, 
buried under a complex of Tertiary volcanics, of both acid 
and basic types. In the Silverton quadrangle (43), for ex- 
ample, this volcanic series is several thousand feet thick and 
consists of tuffs, agglomerates, and lava flows. The more 
or less distinctly horizontal surface volcanics have been pen- 
etrated by later stocks of igneous rock, ranging from gabbro 
nearly to granite in composition, and by many small dikes 
of different types. 

The ore deposits form lodes, stocks, or masses (locally 
called chimneys), and replacement deposits. The lode 



342 



ECONOMIC GEOLOGY OF THE UNITED STATES 



fissures, which form the most important class, have been 
formed at several different periods and show varying strikes, 
but are often of great length, two or three miles being not 
uncommon, while some of the fractures probably extend 
continuously for as much as six miles. . The ore-bearing 

minerals are pyrite 
and sulphides of cop- 
per, silver, lead, or 
zinc, in a gangue of 
quartz, barite, calcite, 
dolomite, rhodochro- 
site, etc. They have 
probably been depos- 
ited from aqueous 
solutions either in 
spaces or pores of 
the rock, or -by re- 
placement. The ores 
are mostly low grade, 
and require careful 
milling to yield profit- 
able returns, but some 
are sufficiently rich to be shipped directly to the smelter. 

Another remarkable development of veins is found around 
Telluride (42) (Fig. 75), one of which, the Smuggler vein, 
has been traced four miles, and cuts the Tertiary volcanics. 
The ores are gold and silver in a gangue of quartz, with 
some rhodochrosite, siderite, calcite, and barite. The ore 
bodies around Ouray (36) differ from those around Silver- 
ton and Telluride in being found in the sedimentaries of 
the region, and form either fissure veins or replacements 




otnd I 7 I IhilMul 
aotu I Z_l baUUM. 

Fig. 75. — Geologic map of Telluride district, 
Colorado, showing outcrop of more important 
veins. After Winslow, Amer. Inst. Min. 
Eng., Trans. XXIX: 290. 



GOLD AND SILVER 



343 



in quartzite or limestone connected with vertical fissures. 
Owing to the different degrees of replaceability shown by 
the wall rocks, the ore bodies present a most varied form. 
Tonopah, Nevada. — Some fine examples of replacement 
deposits are also known in Nevada, an excellent one being 
that found in the recently discovered mining district of 
Tonopah, Nevada (63), which, although opened up only in 
1900, has during the first three years produced over #3,000,000 
worth of gold. The district, which lies in the arid desert 




Fig. 76. — Ideal cross section of rocks at Tonopah, Nev. After Spurr, U.S. 
Geol. Surv., Bull. 225: 108. 

region of Nevada, contains a series of Tertiary lavas and tuffs, 
the former including andesites, dacites, rhyolites, and basalt 
(Fig. 76). The earlier lavas and tuffs have been broken by 
a complex series of faults which have not, however, affected 
the older dacites and closely associated rhyolite necks. Four 
periods of vein formation have been discovered closely fol- 
lowing periods of eruption, and of these only the oldest, 
namely, those found in the earlier andesite, are available 
sources of ore. The veins, which have been formed by 
replacement in sheeted zones and show more or less de- 



344 



ECONOMIC GEOLOGY OF THE UNITED STATES 



velopment of ore shoots, contain quartz with orthoclase, 
and inclose as metallic minerals stephanite and probably 
polybasite. The values are about two sevenths gold and 
five sevenths silver. Subsequent to their formation they 
have been pierced and covered by later volcanic rocks, 
and these, together with the complex faulting, has pro- 
duced most puzzling structural conditions. The Tonopah 
ore deposits are analogous genetically to the Comstock 
lode deposits of Nevada (61). 




Fig. 77. — Section of Comstock lode. D, diorite ; Q, quartz ; V, vein matter in 
earlier diabase (Db) ; H, earlier hornblende andesite; A, augite andesite. 
After Becker. 

Comstock JLode, Nevada. — This lode, which is of historic 
interest, occurs near Virginia City, in southwestern Ne- 
vada, and is a great fissure vein, about four miles long, sev- 
eral hundred feet broad, and branching above, following 
approximately the contact between eruptive rocks, and dip- 
ping at an angle of 35 to 45 degrees. There is abundant 
evidence of faulting, which in the middle portion of the vein 
has amounted to 3000 feet. The lode is of Tertiary age, 
and contains silver and gold minerals in a quartzose gangue. 



GOLD AXD SILVER 345 

One of the peculiar features of the deposit is the extreme 
irregularity of the ore, which occurs in great "bonanzas," 
some of which carried several thousand dollars to the ton. 
The faulting is considered to have been quite recent, and 
the high temperatures encountered in the lower levels of 
the mine indicates that there is probably a partially cooled 
mass of igneous rock at no great depth. 

In former years the enormous output of this mine caused Nevada to 
be one of the foremost silver producers. It was discovered as early as 
1858, and increased until 1877, after which it declined. Many serious 
obstacles w r ere met with in the development of the mine, such that it 
has never become a source of much profit in spite of its enormous output. 
In 1863, at a depth of 3000 feet, the mine was flooded by water of a tem- 
perature of 170° F., due to a break in the clay wall ; and to drain it 
$2,900,000 were spent in the construction of the Sutro tunnel, which was 
nearly four miles long, but by the time it was finished the workings were 
below its depth. A second difficulty was the encountering of high tem- 
peratures in lower workings, these in the drainage tunnel mentioned being 
110° to 114° F. The mine is credited with a total production of $368,- 
000,000. In recent years its output has been slowly increasing again. 

Other occurrences of the propylitic type are found in Gil- 
pin, Boulder, and Clear Creek (48) counties, Colorado. 

In Arizona the Commonwealth Mine of Cochise County 
is probably referable to this group, as is also the Congress 
Mine (19,20). 

Fissure veins associated with * Tertiary eruptives are 
found in Owyhee County, Idaho, in the Monte Cristo dis- 
trict of Washington (88), and the Bohemia district of 
Oregon (70). The auriferous copper veins of Butte, Mon- 
tana, also belong in this group, but since they are more 
important as producers of copper, they are described under 
that head. 



346 ECONOMIC GEOLOGY OF THE UNITED STATES 

Auriferous Gravels (23,29,30). — These form an important 
source of supply of gold, together with a little silver, and, 
although widely distributed, become prominent chiefly in 
those areas in which auriferous quartz veins are abundant. 
So, while they are found in many parts of the Cordilleran 
region, in the Black Hills, and in the Atlantic States, their 
greatest development is in the Pacific coast belt from Cali- 
fornia up to Alaska. 

These auriferous gravels represent the more resistant 
products of weathering, such as quartz and native gold, 
which have been washed down from the hills on whose 
slopes the gold-bearing quartz veins outcrop, and were too 
coarse or heavy to be carried any distance, unless the grade 
was steep. They have consequently settled down in the 
stream channels, the gold, on account of its higher gravity, 
collecting usually in the lower part of the gravel deposit. 

Although the gold-bearing gravels have been derived 
from veins of varying age, the deposition of the gravel 
has rarely occurred in pre-Tertiary times, and some, indeed, 
are of very recent origin. 

The gold occurs in the gravels in the form of nuggets, 
flakes, or dustlike grains, the last being usually hard to 
catch. The nuggets represent the largest pieces, and the 
finding of some very large ones has been recorded from 
time to time in different parts of the world. Two large 
nuggets are recorded from Victoria : one, the " Welcome 
Stranger," weighing 2280 ounces ; and the other, the " Wel- 
come Nugget," weighing 2166 ounces. Since the auriferous 
gravels of the Pacific coast belt are the most important, 
they will be specially referred to. 

These have been derived from the wearing down of the 



GOLD AND SILVER 



347 



Sierras, and are found in those valleys leading off the 
drainage from the mountains. Many were formed during 
the Tertiary period, when the Sierras were subjected to a 
long-continued denudation, while violent volcanic outbursts 
at the close of the Tertiary have often covered the gravels 
and protected them from subsequent erosion. These lava 
cappings are at times 150 to 200 feet thick, as in Table 
Mountain, Tuolumne County. 

Many of the gravel deposits are on lines of former drain- 
age, while others lie in channels still occupied by streams. 
Some show but one streak 
of gold, while in others 
there may be several, some 
of which are on rock 
benches of the valley bot- 
tom (Fig. 78). 

During the early days 
of gold mining in Califor- 
nia the gravels at lower 
levels and in the valley 
bottoms were worked, but as these became exhausted, those 
farther up the slopes or hills were sought. 

In the earlier operations the gravels were washed en- 
tirely by hand, either with a pan or rocker, and this plan 
is even now followed by small miners and prospectors; 
but mining on a larger scale is carried on by one of three 
methods, viz. drift mining, hydraulic mining, and dredging. 

Drift mining is employed in the case of gravel deposits 
covered by a lava cap, a tunnel being run in to the paying 
portion of the bed and the auriferous gravel carried out 
and washed. 




Fig. 78. — Generalized section of old placer, 
with technical terms, a, volcanic cap; 
b, upper lead; c, hench gravel;^, chan- 
nel gravel. After R. E. Browne. 



348 ECONOMIC GEOLOGY OF THE UNITED STATES 

In hydraulic mining, a stream is directed against the 
bank of gravel and the whole washed down into a rock 
ditch lined with tree sections, or into a wooden trough 
with cross pieces or riffles on the bottom. The gold, being 
heavy, settles quickly and is caught in the troughs or 
ditches, while the other materials are carried off and dis- 
charged into some neighboring stream. Mercury is some- 
times put behind the riffles to aid in catching the gold. 

The water which is used to wash down the gravel de- 
posits is often brought a long distance, sometimes many 
miles, and at great expense, bridging valleys, passing 
through tunnels, and even crossing divides, this being 
done to obtain a large enough supply as well as a sufficient 
head of water. 

Owing to the great amount of debris which was swept 
down into the lowlands, a protest was raised by the farm- 
ers dwelling there, who claimed that their farms were 
being ruined ; and it soon became a question which should 
survive, the farmer or the miner, for in places the gravels 
and sand from the washings choked up streams and accu- 
mulated to a depth of 70 or 80 feet. The question was 
settled in 1884 in favor of the farmer by an injunction, 
issued by the United States Circuit Court, which caused 
many of the hydraulic mines to suspend operations; and 
at a later date this was extended by state legislation, 
adverse to the hydraulic mining industry. Owing to this 
setback, hydraulic mining fell to a comparatively unim- 
portant place in the gold-producing industry of California, 
while at the same time quartz mining increased. 

The passage of the Caminetti law now permits hydraulic 
mining, but requires that a dam shall be constructed across 



Plate XXII 











""-*! 


- 


' • • 


«i^l •'■ BC-., ^^v^viiiS 



FiG. 1. — Hydraulic mining of auriferous gravel. The sluice box in the foreground 
is for catching the gold. 




Fig. 2. — An Alaskan placer deposit. 



GOLD AND SILVER 349 

the stream to catch the tailings. This resulted in a revival 
of the industry. 

Dredging consists in taking the gravel from the river 
with some form of dredge. The method, which was first 
practised in New Zealand, has been introduced with great 
success into California, especially on the Feather River, 
near Oroville, and its use has spread to other parts of the 
Cordilleran region. The gravel when taken from the river 
is discharged on to a screen, which separates the coarse 
stones, and the finer particles pass over amalgamated plates, 
tables Avith riffles, and then over felt. 

Formerly much placer gold was obtained by hydraulic 
mining, but the annual supply from this source is slowly 
decreasing, as is that from drift mining, while the returns of 
dredger gold have been continually increasing since 1900, 
being $200,000 in that year and $1,500,000 in 1903. This is 
due to the fact that large areas in Yuba, Sutler. Nevada, Butte, 
and Sacramento counties have been found adapted to dredg- 
ing processes, while the improvement and enlargement of the 
dredging machines has greatly decreased the cost of mining. 

Placer gold is also worked in Idaho, Montana, Oregon, New 
Mexico, and Colorado, all of the deposits except those of the 
last two states having been derived from veins of Mesozoic age. 

Gold also occurs in beach sand of certain portions of the 
Pacific coast of Washington (86), and placer mining has been 
carried on since 1894 ; but the supply of gold, which is ob- 
tained from Pleistocene sands and gravels, is small. 

In arid regions where the gold-bearing sands are largely 
the product of disintegration, and water for washing out the 
metal is wanting, a system known as dry-blowing is some- 
times resorted to. 



350 



ECONOMIC GEOLOGY OF THE UNITED STATES 



BLACK HILLS REGION 

The gold-bearing ores are found chiefly in the northern 
Black Hills, and include (1) auriferous schists in pre- 
Canibrian rocks; (2) Cambrian conglomerates; (3) re- 
fractory siliceous ores ; (4) high-grade siliceous ores ; and 
(5) placers. Of these the first and third are the most 
important. 

The surface placers, being the most easily discovered, were 
developed first, followed by the conglomerates at the base of 




^HHHI SCHIST 



CEVEST VINES 



Fig. 79. — Section of Homestake belt at Lead, S. Dak., showing relation of ancient 
and modern placers to Homestake lode. From Min. Mag. XI: 467. 

the Cambrian. These are found near Lead, occupying depres- 
sions in the old schist surface, and the material is thought 
to have been derived from the reef formed by the Homestake 
ledge in the Cambrian sea. These deposits are of interest 
as being probably the oldest gold placers known in the 
United States. The fact, however, that the matrix of the 
gold-bearing portion of the conglomerate is pyrite rather 
than quartz, and the occurrence of the gold along fractures 
stained by iron, has led some to believe that the gold has 
been precipitated chemically by the action of iron sulphide 
and is not a detrital product. 



Plate XXIII 




+i be 



® =? s 



^s 


01 


Q, 




.. 


CO 

S 




ftq 


O 




A 


- 


co 




^ 


C 


c 




s 


00 


c 


0Q 


2 




^ 


1—' 




© 


^ 














^ 












*? 
























CC 












r5S 












q 






<S 







b 1 



* 1 

2 % 

a ji| 



sl a l 



CD 


. — ' -a 


. *> 


C 


Sb5 


be a 


^ 


C g Ph 


,3-ti 








bS 


S-Pd 


« c, 










tt ^ «r 


co co 



!B l- 00 H « 





s 


<D 


£ 


2 




3 


T3 

a -u 












•£ ^ "5? -0 
o u .£ *i s 




■*> J3 C Jzt 




R ™ % * & 




§ c ^> c £ 








.be ~ -c S § 




Moowa 




rH ©»' CO rt< o 



GOLD AXD SILVER 



351 



Homestake Belt. — The gold ores of the Hoinestake belt 
(76, 77), which are the most important in the Black Hills, oc- 
cur in a broad zone of impregnated schists, containing many 
quartz lenses, alternating with dikes of fine-grained rkyolite, 
which also formed sheets in the Cambrian sediments over- 
lying the schists, and now remain as a resistant cap on many 
of the surrounding ridges. The ore, which is all low grade, 
averaging $5 to $6 per ton, is usually a mixture of quartz, 






\/\-\ / j<--\ i -n 






-/_'. 







fe&d 


ORE 


1 IBM ^ 


mm 


— 

ALGONKIAN 
SCHIST 


te«a| 


CONGLOMERATE 


COMPARATIVELY DOLOMITE 
IMPERVIOUS SLATE 


HARD 
QUARTZITE 


PORPHYRY 



Fig. 80. — Typical section of siliceous gold ores, Black Hills, S. Dak. 
Irving, U. S. Geol. Surv., Prof. Pap. 26. 



After 



pyrite, and occasionally other minerals having no definite 
connection with it, occupying a zone in the Algonkian rocks 
which shows greater hardness, irregularity of structure, and 
mineralization than the surrounding schists. The boundaries 
are poorly defined, and superficial examination may fail to 
distinguish between ore and barren rock. In the upper levels 
the ore seems to be with the dikes, but diverges from them 
in depth, and there is apparently no genetic relation between 
the two. In the earlier days the ore encountered was oxidized 
and free-milling, but the appearance of sulphides with depth 



352 ECONOMIC GEOLOGY OF THE UNITED STATES 

has necessitated the introduction of the cyanide method of 
extraction. In spite of the low grade of its ores the Home- 
stake mine, due to proper management, stands out as one 
of the richest mines of the world, its monthly production 
amounting to about 1300,000 (Curie). The ore was origi- 
nally worked as an open cut (PI. XXIII), but later by 
underground methods. 

Siliceous Cambrian Ores. — A second important type is 
the refractory siliceous Cambrian ore found in the region 
between Yellow Creek and Squaw Creek, and yielding about 
two thirds as much gold as the Homestake. The deposits, 
which occur as replacements in a siliceous dolomite, are found 
at two horizons, one immediately overlying the basal Cam- 
brian quartzite, and the other near the top of the Cambrian 
series. The ore forms flat banded masses known as shoots, 
and varying in width from a few inches to 300 feet. It is 
overlain by shale or eruptive rock, and associated with a 
series of vertical fractures, made prominent by a slight silici- 
fication of the wall rock. These fractures, which are termed 
verticals, are supposed to have conducted the ore-bearing 
solutions. 

The ore is a hard, brittle' rock, composed of secondary 
silica, with pyrite and fluorite, and at times barite, wolfram- 
ite, stibnite, and jarosite. Its contents range from $3 or $4 
per ton to in rare cases 1100 per ton, with an average of 
$11. Other, but less important, siliceous ores occur in the 
Carboniferous rocks. 

Michigan Region (55) . — A small amount of gold has been 
found in a quartzose zone in schists, near Marquette, Mich- 
igan, but the area is of little importance. 

Eastern Crystalline Belt (82) . — Gold, with some silver, has 



GOLD AND SILVER 353 

been found in the rocks of this belt from Vermont to Alabama, 
but the deposits are of little importance except in North 
Carolina (68), South Carolina (74), Georgia (49, 50), and Ala- 
bama (3). In this belt the ore occurs as auriferous pyrite, 
in quartz veins, as impregnations in metamorphic rocks, or 
in placers derived from either of the foregoing groups. The 
last-named type is practically exhausted. Of the other types, 
there are many occurrences, in all of which the ore exists in 
variable quantities, but is of very low grade, so that to be 
profitable the deposits must be worked on a large scale by 
proper methods. In many localities the free gold of the 
oxidized portion of the ore body has been worked out and 
the mine abandoned. 

The deposits are in many instances associated with in- 
trusives, some of which are metamorphosed, still they bear 
no genetic relation to them, being frequently of later origin. 
They are usually classed as pre-Cambrian, but some may be 
of later age. 

Alaska (14). — Although gold has been known to occur 
in Alaska since the early part of the century, and was 
even worked in 1860, its production is not definitely stated 
until 1880, when it was added to the list of gold-producing 
regions, with an output of $6000, which since that time has 
increased many times over, but not steadily, until in 1903 it 
amounted to $8,614,700. 

The first gold was discovered on the islands of the Alex- 
ander Archipelago and along the adjoining coast, but sub- 
sequently prospectors found their way into the interior, the 
first strikes there being made in British Columbia near the 
head of the Stikine River. These were followed by dis- 
coveries in the Yukon Valley, especially along some of the 

2a 



354 



ECONOMIC GEOLOGY OF THE UNITED STATES 



tributaries known as Birch Creek, Mission Creek, and 
Forty Mile Creek. In 1896 still richer discoveries were 
made along the Klondike River, and within one year the 
yield of this region had exceeded the purchase price of 
Alaska. Other discoveries have since followed rapidly. 
The gold deposits of Alaska are of two types, viz. quartz 




BORMAr 4 CO., N. r. 



Fig. 81. — Map showing mineral deposits of Alaska as far as known. After 
Brooks, U. S. Geol. Surv., Bull. 259. 

veins and placers. The former are prominent along the 
coast, and the most important producer is the Treadwell 
group of mines on Douglas Island, southeast of Juneau (14). 
The geology of this region bears in many ways a strong 
resemblance to the California gold belt, and is probably of 
similar age. The section involves a series of steeply dipping 
slates and greenstone and diorite dikes (Fig. 83). The ore 



GOLD AND SILVER 



355 



bodies are dikes of albite-diorite, permeated with metallic 
sulphides and carrying small amounts of gold (14), with a 
hanging wall of greenstone and a foot wall of black slate. 
The veinlets, which are thought to have been formed by 
shearing stresses incident to epeirogenic movements, occur 
in two sets of fractures at right angles to each other. 
Spencer believes that the mineralization has been caused 
by hot ascending solutions of possibly magmatic origin. 




EDDED 



GR EENSTON< 



t^SS^E 



Fig. 82. — Sketch map of Douglas Island, Alaska. After Spencer, U. S. Geol. 
Surv., Bull. 259:71. 

Secondary concentration is not in evidence, and it is 
thought that the depth to which the ores can be worked 
will depend more on the increased cost of mining at great 
depths rather than on exhaustion of the ore. At present 
an almost continuous ore body has been developed for 
3500 feet. 

The placer deposits have been found in many parts of 
Alaska, but the two regions which have yielded the largest 
amount are the Yukon region (16) and the Seward Penin- 
sula (14, 15), the latter being now the first. 



356 ECONOMIC GEOLOGY OF THE UNITED STATES 

Gold was discovered in the Forty Mile district of the 
Yukon in 1886, and caused a stampede for this region; but 
the deposits of the Klondike did not become known until 
1896, and their discovery was followed by a rush of gold 
seekers that eclipsed all previous ones. Indeed, it is said 
that by 1898 over 40,000 people were camped out in the 
vicinity of the present site of Dawson. 

The Klondike region proper is situated on the eastern 
side of the Yukon River, and the richer deposits found 
have been on the Canadian side of the boundary. The 





/ fc" I t " MSB JMSBm / DIORITE 


i/jgi 

SLATE 


fir/, 

GREENSTONE 


SW 

BOWLDER 
CLAY 


mii/ii/u/, 

SCALE 1,050 FEET=1 INCH 


Wll\ 


1*51 


kH 









Fig. 83. — Cross section through Alaska Tread well mine on northern side of 
Douglas Island. After Spencer, U. S. Geol. Surv., Bull. 259 

gold has collected either at the bottom of the gravel in the 
smaller streams tributary to the Yukon, or else in gravels 
on the valley sides, this latter occurrence being known as 
bench gravel. The metal is supposed to have been derived 
from the quartz veins found in the Birch Creek, Forty Mile, 
and Rampart series of metamorphic rocks lying to the east. 
Up to the end of 1902 the total production of the Klondike 
is stated to have been $80,000,000. The annual output has, 
however, decreased, and mining in that region has settled 
down to a more permanent basis. Gravels running under 
$9 per cubic 3^ard cannot be worked at a profit, because the 
difficulties and expenses of running in such a region are 



GOLD AND SILVER 357 

great, and form an interesting comparison with conditions 
in California, where gravel carrying 25 cents per yard is 
considered good, while that running as low as 5 cents per 
yard can be worked (18). 

Since the discovery of the rich gold gravels on the Yukon, 
auriferous gravels have been developed in many other parts 
of Alaska, where they are being more or less actively worked 
(Fig. 81), but of these various finds those in the Seward 
Peninsula, which is now the largest producer, have been 
the most important. 

The first of the localities discovered in the last-mentioned 
region was Cape Nome (15), which for a time proved to be a 
second Klondike. The gold was discovered here on Anvil 
Creek, and the following year in the beach sands where 
Nome now stands. These discoveries caused another north- 
ward stampede, which resulted in the rapid exhaustion of 
the beach sands ; but other deposits were found farther 
inland near Nome, as well as the other localities on the 
Seward Peninsula. Some quartz veins are also worked. 
Ophir Creek is now the largest producer on the Seward 
Peninsula. Up to the end of 1902 the Seward Peninsula 
had produced $20,000,000 in gold, and in 1903 the produc- 
tion of the Nome region is given as $1,437,449. 

Uses of Gold. — Gold is chiefly used for coinage, orna- 
ments, and ornamental utensils. It is also employed to 
a considerable extent in dentistry and in an alloy for the 
better class of gilding. 

Its value for use in the arts depends on its brightness, 
freedom from tarnish, and its ductility and malleability, 
which permit it to be easily Avorked. As pure 24-carat 



358 



ECONOMIC GEOLOGY OF THE UNITED STATES 



gold is too soft for use, it is alloyed with a small amount 
of some other metal, such as copper, to gain hardness. 

Uses of Silver. — This metal was formerly of much im- 
portance for coinage, but is much less so now. It is, 
however, widely employed in the arts for making jewelry 
and utensils such as tableware. Its salts are of more 
or less value in medicine and in photography. Its bright- 
ness and white color are valuable properties when the metal 
is used, but, unlike gold, it tarnishes somewhat readily when 
exposed to sulphurous gases. There are a number of alloys 
of silver, those with gold and copper, respectively, being 
of importance. 

Production of Gold and Silver : — 

Production of Gold and Silver in the United States from 

1845 to 1903 



Year 


Total 


Gold 


Silver 
(Coining Value) 


1845 

1855 

1865 

1875 

1885 

1895 

1900 

1901 

1902 

1903 


11,058,327 

55,050,000 

64,475,000 

65,100,000 

83,400,000 

118,661,000 

153,704,495 

150,054,500 

151,757,575 

143,797,760 


$1,008,327 
55,000,000 
53,225,000 
33,400,000 
31,800,000 
46,610,000 
79,171,000 
78,666,700 
80,000,000 
73,591,700 


$50,000 
50,000 
11,250,000 
31,700,000 
51,600,000 
72,051,000 
74,533,495 
71,387,800 
71,757,575 
70,206,060 



The production by states for 1903 is given below, and 
shows well the overwhelming importance of the Cordil- 
leran region : — 



GOLD AND SILVER 



359 



Production and Value of Gold and Silver in the United 
States in 1903, by States 





Gold 


Sii/ 


PER 


Total 












(Silver at 










Commercial 


Commercial 




Quantity 


Value 


Quantity 


Value 


Value) 




Fine oz. 


Dollars 


Fine oz. 


Dollars 


Dollars 


Alabama . . 


213 


4,400 






4,400 


Alaska . . . 


416,738 


8,614,700 


143,600 


77,544 


8,692,244 


Arizona . . . 


210,799 


4,357,600 


3,387,100 


1,879,034 


6,186,634 


California . . 


779,057 


16,104,500 


931,500 


503,010 


16,607,510 


Colorado . . 


1,090,376 


22,540,100 


12,990,200 


7,014,708 


29,554,808 


Georgia . . . 


3,000 


62,000 


400 


216 


62,216 


Idaho . . . 


75,969 


1,570,400 


6,507,400 


3,513,996 


5,084,396 


Kansas . . . 


468 


9,700 


97,400 


52,596 


62,296 


Maryland . . 


24 


500 






500 


Michigan . . 






50,000 


27,000 


27,000 


Montana . . 


213,425 


4,411,900 


12,642,300 


6,826,842 


11,238.742 


Nevada . . . 


163,892 


3,388,000 


5,050,500 


2,727,270 


6,115.270 


New Mexico . 


11,833 


244,600 


180,700 


97,578 


342,178 


North Carolina 


3,411 


70,500 


11,000 


5,940 


76,440 


Oregon . . . 


62,411 


1,290,200 


118,000 


63,720 


1,353,920 


South Carolina 


4,872 


100,700 


300 


162 


100,862 


South Dakota . 


330,243 


6,826,700 


221,200 


119,448 


6,946,148 


Tennessee . . 


38 


800 


13,000 


7,020 


7,820 


Texas . . . 






454.400 


245,376 


245,376 


Utah .... 


178,863 


3,697,400 


11,196,800 


6,046,272 


9,243,672 


Virginia . . 


654 


13,500 


9,500 


15,130 


18,630 


Washington . 


13,539 


297,900 


294,500 


159,030 


438,930 


Wyoming . . 


175 


3,600 


200 


108 


3,708 


Total . . 


3,560,000 


73,591,700 


54,300,000 


29,322,000 


102,913,700 



Mr. Lindgren (80) has recently given a most interesting 
and valuable classification of the figures of gold and silver 
production, grouped according to the kind of ores from 
which they have been derived. These are given below, 
and indicate that the Tertiary quartz veins yield the 
largest amount of gold, and the lead ores the greatest 
quantity of silver. 



360 



ECONOMIC GEOLOGY OF THE UNITED STATES 



Production of Gold and Silver in 1904 according to 
Kinds of Ore 





Gold 
Fine Ounces 


Silver 
Fine Ounces 


Placers 

Quartzose gold and silver ores — 

Pre-Cambrian quartz veins 

Mesozoic quartz veins . 

Tertiary quartz veins 

Copper ores 


619,700 

264,000 

1,045,000 

1,727,000 

206,000 

222,500 


64,000 

79,000 

860,000 

11,000,000 

18,600,000 

23,000,000 


Lead ores 






4,086,200 


53,603,000 



World's Production of Gold and Silver in 1903 



North and Central America 

Australia 

Africa 

Europe 



Asia . . . . 

South America 



Total 



Gold 



979,000 
89,210,100 
67,998,100 
27,117,800 
25,434,000 
10,788,200 



$325,527,200 



Silver 



£70,235,500 

5,228,700 

185,300 

8,182,100 

359,100 

7,848,900 



)2,039,600 



Total 



$175,214,500 
94,438,800 
68,183,400 
35,299,900 
25,793,100 



$417,566,800 



REFERENCES ON GOLD AND SILVER 

General. 1. Blake, Amer. Inst. Min. Engrs., Trans. XXVI : 290, 1897. 
(Gold in igneous rocks.) 2. Cumenge and Robellaz, L'Or dans la 
nature (Paris, 1898). 3. Curie, The Gold Mines of the World 
(London, 1902). 4. Don, Amer. Inst. Min. Engrs., Trans. XXVII : 
564, 1898. (Genesis of certain auriferous lodes.) 5. Emmons, 
Amer. Inst. Min. Engrs., Trans. XVI : 804, 1888. (Structural rela- 
tions of ores.) 6. Kemp, Min. Indus., VI: 295, 1898. (Telluride 
ores.) 7. Liversidge, Amer. Jour. Sci., XIV: 466, 1902. 8. Mer- 
rill, Amer. Jour. Sci., 1 : 309, 1896. (Gold in granite.) 9. Pearce, 
Ores of Gold, etc., Colo. Sci. Soc. Proc, III: 237. 10. Rickard, 
Min. and Sci. Pr., LXXVII : 81 and 105, 1898. (Minerals ac- 



GOLD AND SILVER 361 

companying gold.) 11. Spurr, Eng. and Min. Jour., LXXVI : 
500, 1903. (Gold in diorite.) 12. Spurr, Eng. and Min. Jour., 
LXXVII : 198, 1904. (Native gold original in metamorphic gneis- 
ses.) —Alabama: 13. Brewer, Ala. Geol. Surv., Bull. 5, 1896; Phil- 
lips, Ala. Geol. Surv., Bull. 3, 1892. — Alaska : 14. Brooks and 
others, U. S. Geol. Surv., Bull. 259, 1905. (Mineral resources.) 
15. Schrader and Brooks, Amer. Inst. Min. Engrs., Trans. XXX : 
236, 1901. (Cape Nome.) 16. Spurr, U. S. Geol. Surv., 18th Ann. 
Rept., Ill : 101, 1898. (Yukon district.) 17. See also various papers 
on Alaska in U. S. Geol. Surv., Bull. 213, 1903, and Bull. 225, 1901. 
18. Penrose, Eng. and Min. Jour., LXXVI: 807, 852, 1903.— 
Arizona : 19. Blandy, Amer. Inst. Min. Engrs., Trans. XI : 286, 1882. 
(Prescott district.) 20. Comstock, Amer. Inst. Min. Engrs., Trans. 
XXX: 1038, 1901. (Geology and vein phenomena.) 21. Pratt, 
Eng. and Min. Jour., LXXI1I : 795, 1902. Literature on Arizona 
gold ores, especially of recent character, is scarce. 22. See reports 
of Director of Mint. — California: 23. Browne, Calif. State Min. 
Bur., 10th Ann. Rept.: 435. (River gravels.) 24. Diller, U. S. 
Geol. Surv., Bull. 260: 45, 1905. (Indian Valley region.) 25. Fair- 
banks, Calif. State Min. Bur., X: 23, 1890, and XIII: 665, 1896. 
(Mother Lode district.) 26. Lindgren, U. S. Geol. Surv., 17th Ann. 
Rept., II : 1, 1896. (Nevada City and Grass Valley.) 27. Lindgren, 
Geol. Soc. Amer., Bull. VI: 221, 1895. (Gold quartz veins.) 
28. Lindgren, U. S. Geol. Surv., 14th Ann. Rept., II: 243, 1894. 
(Ophir.) 29. Lindgren, U. S. Geol. Surv., Bull. 213: 64, 1903. 
(Neocene river gravels.) 30. Turner, Amer. Geol., XV : 371, 1895. 
(Auriferous gravels.) 31. See also various annual reports of Calif. 
State Mineralogist. — Colorado: 32. Comstock, Amer. Inst. Min. 
Engrs., Trans. XV: 218, 1886, and XI: 165, 1882. (Geology and 
vein structure, southwestern Colo.) 33. Emmons, Eng. and Min. 
Jour., XXXV : 332, 1883. (Summit district.) 34. Emmons, U. S. 
Geol. Surv., 17th Ann. Rept., II : 405, 1896. (Custer Co.) 35. Farish, 
Colo. Sci. Soc, Proc. IV : 151, 1892. (Rico.) 36. irving, U. S. 
Geol. Surv., Bull. 260 : 50, 1905. (Ouray.) 37. Irving, U. S. Geol. 
Surv., Bull. 260 : 78, 1905. (Lake City.) 38. Kedzie, Amer. Inst. Min. 
Engrs., Trans. XV : 570, 1886. (Red Mt.) 39. Lindgren and Ran- 
some, U. S. Geol. Surv., Bull. 256, 1905. (Cripple Creek.) 40. Pen- 
rose and Cross, U. S. Geol. Surv., 16th Ann. Rept., II: 111, 1895. 
(Cripple Creek.) 41. Porter, Amer. Inst. Min. Engrs., Trans. XXVI : 
449, 1897. (Telluride.) 42. Purington, U. S. Geol. Surv., 18th Ann. 
Rept., Ill : 751, 1898. (Telluride.) 43. Ransome, U. S. Geol. Surv., 
Bull. 182, 1901. (Silverton.) 44. Rickard, Min. Indus., II: 325, 
1894, and IV : 315, 1895. 45. Rickard, Amer. Inst. Min. Engrs., 



362 ECONOMIC GEOLOGY OF THE UNITED STATES 

Trans. XXX : 367, 1901. (Cripple Creek.) 46. Schwartz, Amer. Inst. 
Min. Engrs., Trans. XVIII : 139, 1890. (Cripple Creek.) 47. Skewes, 
Amer. Inst. Min. Engrs., Trans. XXYI : 553, 1897. (Cripple Creek.) 
48. Spurr, U. S. Geol. Snrv., Bull. 260: 99, 1905. (Georgetown.) — 
Georgia : 49. Eckel, U. S. Geol. Surv., Bull. 213 : 57, 1903. (Dahlonega 
district.) 50. Yeates, McCallie, and King, Ga. Geol. Surv., Bull. 4 a, 

1896. — Idaho: 51. Lindgren, U.S. Geol. Surv., 20th Ann. Rept., 
Ill: 75, 1900. (Silver City, De Lamar Co.) 52. Lindgren, U. S. 
Geol. Surv., 18th Ann. Kept., Ill : 625, 1898. (Idaho Basin and 
Boise Ridge.) — Kansas : 53. Lindgren, Eng. and Min. Jour., LXXIV : 
111, 1902. (Tests for gold and silver in shales.) — Maryland: 
54. Weed, U. S. Geol. Surv., Bull. 260 : 128, 1905. (Great Falls.) 

— Michigan : 55. Wadsworth, Ann. Kept., 1892, Mich. State Geologist. 

— Minnesota : 56. Winchell and Grant, Minn. Geol. and Nat. Hist. 
Surv., XXIII : 36, 1895. (Rainy Lake district.) — Montana : 57. Lind- 
gren, U. S. Geol. Surv., Bull. 213 : 66, 1903. (Bitter Root and Clear- 
water Mts.) 58. Weed, U. S. Geol. Surv., Bull. 213: 88, 1903. 
(Marysville.) 59. Weed and Barrell, U. S. Geol. Surv., 22d Ann. 
Kept., II : 399, 1902. (Elkhorn district.) 60. Weed and Pirsson, 
U. S. Geol. Surv., 18th Ann. Kept, III: 589, 1898. (Judith Mts.) 

— Nevada: 61. Becker, U. S. Geol. Surv., Mon. Ill, 1882. (Corn- 
stock Lode.) 62. Lord, U. S. Geol. Surv., Mon. IV, 1883. (Comstock 
mining.) 63. Spurr, U. S. Geol. Surv., Bull. 227, 1904, and Bull. 
260 : 140, 1905. (Tonopah.) 64. Spurr, U. S. Geol. Surv., Bull. 225 : 
118, 1904, and Bull. 260 : 132, 1905. (Gold fields.) 65. Spurr, U. S. 
Geol. Surv., Bull. 225 : 111, 1904. (Silver Peak quadrangle.) 66. See 
also annual reports of Director of Mint. — New England : 67. Smith, 
U. S. Geol. Surv., Bull. 225: 81, 1904. (Me. and Vt.) — North 
Carolina : 68. Nitze and Hanna, N. Ca. Geol. Surv., Bulls. 3 and 10. 

— Oklahoma: 69. Bain, U. S. Geol. Surv., Bull. 225: 120, 1904. 
(Wichita Mts.) — Oregon : 70. Diller, U.S. Geol. Surv., 20th Ann. 
Kept., Ill: 7, 1900. (Bohemia district.) 71. Kimball, Eng. and 
Min. Jour., LXXIII: 889, 1902. (Bohemia district.) 72. Lindgren, 
U. S. Geol. Surv., 22d Ann. Rept., II: 551, 1901. (Blue Mts.) 
73. See also bulletin on Oregon Mineral Resources issued by Uni- 
versity of Oregon. — South Carolina : 74. Thies and Mezger, Amer. 
Inst. Min. Engrs., Trans. XIX : 595, 1891. (Haile Mine.) See also 
No. 82. — South Dakota: 75. Carpenter, Amer. Inst. Min. Engrs., 
Trans. XVII : 570, 1888. 76. Irving, U. S. Geol. Surv., Bull. 225 : 
123, 1904, and U. S. Geol. Surv., Prof. Paper 26, 1904. (N. Black 
Hills.) 77. O'Harra, S. Dak. Geol. Surv., Bull. 3, 1902. (Black 
Hills.) 78. Smith, Amer. Inst. Min. Engrs., Trans. XXVI: 485, 

1897. (Cambrian ores.) — United States: 79. Lindgren, Amer. Inst. 



GOLD AND SILVER 363 

Min. Engrs., Trans. XXXIII: 790, 1903. (N. Amer. production 
and geology.) 80. Lindgreu, U. S. Geol. Surv., Bull. 260: 82, 1905. 
81. Mtze and Wilkens, Amer. Inst. Min. Engrs., Trans. XX V : 691, 
1896. (Appalachians.) 82. Pratt, Eng. and Min. Jour., LXX1V : 
'241, 1902. (S. Appalachians.) 83. Ransorne, Min. Mag., X: 7, 
1901. See also annual reports on Precious Metals, issued by Director 
of Mint, the Mineral Resources issued by U. S. Geol. Surrey, the 
Mineral Industry, and Census Report on Mines and Quarries, 1902. 
— Utah : 84. Spurr, U. S. Geol. Surv., 16th Ann. Rept., II : 343, 1895. 
(Mercur.) See also annual reports of Director of Mint, all of which 
contain much general information, partly of statistical character; 
also references under Silver-Lead. 85. "Warren, Eng. and Min. Jour. 
LXVIII : 455, 1899. (Daly- West Mine.) — Vermont : See New Eng- 
land. —Washington : 86. Arnold, U. S. Geol. Surv., Bull. 260: 154, 
1905. (Beach placers.) 87. Smith, Eng. and Min. Jour., LXXIII : 
379, 1902. (Mt. Baker district.) 88. Spurr, U. S. Geol. Surv., 22d 
Ann. Rept., II: 777, 1901. (Monte Cristo.) 



CHAPTER XVIII 
SILVER-LEAD ORES 

The Silver-Lead Ores form a large class, which are widely 
distributed in the Cordilleran region, and not only supply 
most of the lead mined in the United States, but in ad- 
dition may also and often do carry variable quantities of 
silver, gold, and copper. 

The deposits as a whole present a variety of forms. The 
associated rocks are often faulted, and the ore bodies are 
commonly oxidized above so that the altered portions re- 
quire different metallurgical treatment from the sulphide 
ores found below. Secondary enrichment has in some cases 
raised the grade of the ore. Deposits of this class are 
prominent in Colorado, Idaho, and Utah, but are also known 
in New Mexico, Montana, Wyoming, Nevada, Arizona, Cali- 
fornia, and South Dakota. Idaho is the largest producer of 
silver-lead ores, but they average only one third silver, 
while those of Colorado average three quarters silver, and 
those of Utah about two thirds silver. A few of the more 
prominent occurrences are mentioned. 

Leadville District, Colorado (1, 7). — This region lies in the 
Mosquito range at the headwaters of the Arkansas River in 
south central Colorado, while the town of Leadville is situ- 
ated in an old lake basin on the west side of the range. 
The latter is composed of crystalline rocks, Paleozoic sedi- 

364 



SILVER-LEAD ORES 365 

merits, and igneous intrusions, the last in part conforming 
to the bedding planes of the sedimentary rocks. The 
Paleozoic section alone is over 5000 feet and involves the 
following members : — 

Upper Carboniferous limestone . . 1000 to 1500 feet. 

Weber shales and sandstone . . . 2000 feet. 

Oldest or white porphyry .... 

Carboniferous blue limestone (chief 

ore-bearing stratum) 200 feet. 

Gray porphyry 

( Quartzite 40 feet. 

Silurian \ . 

[ White limestone .... 160 feet. 

Cambrian quartzite 150 to 200 feet. 

The rocks on the western side of the Mosquito range are 
folded and faulted, this having taken place during late Cre- 
taceous times, when the Rocky Mountains were uplifted, and 
subsequent to the intrusion of the igneous rocks. It is con- 
sidered that the latter stimulated the ascension of the ore- 
bearing solutions, the ore being commonly deposited on the 
under side of the porphyry sheets and in contact with the 
blue Carboniferous limestones. Later developments have 
shown its presence along some of the other contacts. The 
unaltered ore is argentiferous galena with some native gold, 
but within the zone of oxidation the galena is changed to 
carbonate and sulphate, with silver chloride and at times 
containing considerable limonite. The gangue is calcite, 
barite, and chert. 

The older mines are mostly east of the city on Fryer, Car- 
bonate, and Iron Hill, but in recent years the continuation of 
the deposits has been found under the city. 



366 



ECONOMIC GEOLOGY OF THE UNITED STATES 



The origin of the ores has been discussed by several geolo- 
gists, among them Emmons and Blow (1, 7). The former 
believes that the ores were originally deposited as sulphides 
from aqueous solutions ascending from 
some deep source, and by a process in- 
S volving metasomatic interchange, the 
§ ore-bearing solutions following the con- 
£j tact because it happened to form a 
§ good channel. 

g For many years the oxidized ores of 
^ the Leadville district have been an 
« important source of material for the 
§ smelters; but latterly the silver ores 
». have shown signs of exhaustion, and 
^ their place has been taken to some 
-g extent by the discovery of gold ore to 
| the east of the town, as well as of zinc 
2 sulphides at greater depths and the 
£ shipment of larger quantities of iron 
^ and manganese ores than formerly. 

m 

O 

<& Even in former years Leadville was a mining 

•2 camp of great importance, having indeed given 
3d Colorado its first serious start as a mining state. 
S From an area of about a square mile the output 
| of silver was for a number of years greater than 
35 that of any foreign country except Mexico, 
2 and during the same period the production of 
lead was nearly equal to that of England and 
greater than that of any European country 
excepting Spain and Germany. Although regarded originally as a 
silver camp, it really ceased being such nearly ten years ago, and is now 
an important producer of at least eight metals, of which five or six are 



SILVER-LEAD ORES 367 

sometimes all obtained from the same group of properties. It will thus 
be seen that the successful marketing of one may affect all the others. 
Leadville began as a gold camp in 1860, when a placer deposit of gold 
was found in a gulch near there and several million dollars' worth of 
metal were extracted, resulting in the establishment of a flourishing 
town called Oro, which, however, soon lost its importance when the gold 
began to be exhausted. Not until 1875 was the carbonate of lead, which 
has since been so important, actually recognized. 

That Leadville is no longer entirely a lead-silver camp is evident 
from the fact that, in 1901, of the 850,000 long tons of ore mined, 35,000 
tons were zinc ores, 70,000 tons manganese iron ores, and the remainder 
lead and copper smelting ores. 

Aspen, Colorado (15). — Here again the ores are oxidized 
and occur in highly folded and faulted Carboniferous lime- 
stone, although the section involves rocks ranging in age from 
Archaean to Mesozoic. Two quartz porphyries, one at the 
base of the Devonian, the other in the Carboniferous, are 
present, but bear no special relation to the ore. 

At the close of the Cretaceous the rocks were folded into 
a great anticline, with a syncline on its eastern limit, which 
passed into a great fault along Castle Creek west of the 
mines. Contemporaneous with the folding there were also 
produced two faults parallel to the bedding of the Carbonif- 
erous dolomite, while at the same time much cross faulting 
occurred. The ore is found chiefly at the intersection of 
these two sets of fault planes, and Spurr considers that the 
ore-bearing solutions followed the bed faults. 1 

On account of the intimate association of the dolomite, 

quartz, and barite with the ore their origin is considered as 

similar. 

, 1 Weed has suggested that this accumulation of ore at the intersection of 
fault planes is the result of secondary enrichment, rather than of primary 
concentration. 



368 



ECONOMIC GEOLOGY OF THE UNITED STATES 




7 



The ores are peculiarly free from other metals except 
lead, and the rich polybasite (Ag 9 SbS 6 ) ores of Smuggler 

Mountain do not contain 



even this. 

The mining camp of 
Aspen started in 1879, 
but its development for 
a time was much re- 
tarded by lawsuits. The 
richer ore bodies were 
not discovered until 
1884, and then by un- 
derground exploration, 
for owing to the heavy 
mantle of glacial gravels 
their outcrops were hid- 
den. Since also the 
ore carries no iron or 
manganese, as do the 
Leadville ores, its out- 
crop may be incon- 
spicuous. 




GLACIAL DRIFT 
\^A WEBER FORMATION 



IlJ PARTING QUARTZITE 
yV l\ YULE FORMATION 



ORE 

LEADVILLE DOLOMITE 



iJ SAWATCH FORMATION' 
\££\ GRANITE 
r**\ QUARTZ PORPHYRY 

Section of ore body at Aspen, Colo. 



Fig. 85, 
After Spurr, U.S. Geol. Sum., Mon. XXXI. 



The railroads did not 
reach the camp until 1887, 
so that during the first few 
years of its history the ore had to be carried out on burros. 

In both Aspen and Smuggler mountains long tunnels have been run 
for drainage and hauling purposes. The Cowenhoven tunnel, which is 
the largest of these, is over 8300 feet long, and taps a number of mines. 
Aspen was one of the first mining camps in the West to install electric 
machinery for hoisting, haulage, etc., and the current was cheaply sup- 
plied by the neighboring water power. One shaft 1000 feet deep is 
operated electrically. 



Plate XXIV 




Fig. 1. — General view of Rico, Colo., and Enterprise group of mines. 




Fig. 2. — Ontario mine, Park City, Utah. 



SILVER-LEAD ORES 



369 



At the present day the larger ore bodies are worked out, but the camp 
is still an active producer. From 1881 to 1895 it produced $63,653,989 
worth of silver. 

Other Occurrences. — Argentiferous lead ores also occur in 
the Ten Mile district (8), in Chaffee County, and along the 
Eagle River (11). They 
are also known in Red 
Mountain (10 a), and in 
Rico Mountain, Dolores 
County (4, 12, 13). In the 
last-mentioned region the 
mountains, which are 
the remains of the struc- 
tural dome arising above 
the Dolores plateau lying 
in the San Juan region, 
contain a series of sedi- 
mentary beds ranging 
from Algonkian to Juras- 
sic in age, which have 
been uplifted partly by 
the intrusion of igneous 




SANDY SHALE 



BLACK SHALE 
BLANKET 

BLANKET LIMESTONE 
BLACK SHALE 
SANDSTONE 
SANDY SHALE 



SANDSTONE 



SANDY SHALE 

SANDSTONE 
SANDY SHALE 

SANDSTONE 



SANDY SHALE 



SANDY SHALE 



Fig. 86. —Diagrammatic section across a 
northeasterly lode at Rico, Colo., showing 
" blanket " of ore. After Ransome, U. S. 
Geol. Surv., 22d Ann. Rept., II. 



rocks, as stocks, sills, and dikes, and partly by upthrows due 
to faulting. 

The ore occurs as lodes, replacements in limestone, stocks, 
and blankets, the last consisting usually of deposits lying 
parallel to the planes of bedding or to the sheets of igneous 
rock, and known locally as "contacts," although not such 
in the true sense. 

The four types of deposit mentioned may pass into each 
other. Most of the ore in the district has, however, 
2b 



370 



ECONOMIC GEOLOGY OF THE UNITED STATES 



come from the blankets, and the bulk of this has been 
found in the Carboniferous, especially in the Hermosa 
formation, a striking feature of the deposits being their 
limited vertical range. 

The ores are primarily galena, often highly argentifer- 
ous and associated with rich silver-bearing minerals. In 

many deposits the more or 
less complete oxidation of 
the silver ores has resulted 
in powdery masses, often 
very rich in silver. Below 
the zone of oxidation, the 
veins have not been success- 
fully worked. 

The bulk of the ores can 
be roughly divided into py- 
ritic ores, usually low grade, 
and silver-bearing galena 
ores, sometimes containing 
rich silver minerals. Quartz 
is the commonest gangue 
mineral, but the beautiful 
pink rhodochrosite is also 
conspicuous. 

The ore deposition is be- 
lieved to be closely associated with the igneous intrusions 
of the district, especially with the later ones. 

Most of the ore produced in the Rico district has been 
shipped crude or smelted in Rico without mechanical 
concentration. 

Park City, Utah (2), which is located on the eastern 




E3- 



Fig. 87. — Vein filling a fault fissure, 
Enterprise mine, Rico, Colo. After 
Richard, Amer. Inst. Min. Eng., 
Trans. XXVI: 927. 



SILVER-LEAD ORES 371 

slope of the Wasatch range, about 25 miles southeast of 
Salt Lake City, has made Summit County famous as one 
of the important mining centers of this country, as there 
are here large bodies of rich silver-lead ores carrying minor 
values of gold and copper. The success of this camp, 
therefore, depends more or less on the condition of the 
silver and copper industry. 

The geological section involves a series of limestones, 
sandstones, and shales, chiefly of Carboniferous age, and 
having an aggregate thickness of over 6000 feet, with a 
general dip of 30 to 40 degrees northwest, and traversed 
by many fissures, faults, and intrusions, the last being of 
either dioritic or porphyritic types. The ores, which in 
the oxidized zone are cerussite, anglesite, azurite, mala- 
chite, etc., and in the sulphide zone are galena, tetrahe- 
drite, and pyrite, occur either as lodes or fissures, or as 
bedded deposits in limestones. The latter, which supply 
most of the ore, form replacements in certain strata of 
both the upper Carboniferous and Permocarboniferous, and 
lie between siliceous members as walls. Both types of ore 
deposit are frequently associated with porphyry. 

The fissures carry either silver or lead with or without 
zinc, and copper or gold with some silver. The replace- 
ment ores of the limestones hold silver and lead chiefly. 
The contact ores contain copper and gold with or without 
silver, and form irregular bodies in metamorphic limestone 
adjacent to the igneous rock. The ordinary crude ore 
carries 50 to 55 ounces silver, 20 per cent lead, .04 to .05 
ounce gold, 1.5 per cent copper, 10 to 18 per cent zinc. 
Silver is obtained in the proportion of 3 ounces silver to 
each per cent iron, 1 ounce silver to each per cent lead, 



372 ECONOMIC GEOLOGY OF THE UNITED STATES 

and .5 ounce silver to each per cent zinc. Bonanzas are 
known. The low-grade ores are treated at the concen- 
trating mill, while the rich ores are shipped to the smelter. 

Tintic District, Utah (16). — This district lies in the Tintic 
Mountains, about 65 miles southwest of Salt Lake City. 
The ores are argentiferous galena, with small amounts of 
copper, the average assaj^ of 240,000 tons being .6 per 
cent copper and 13.5 lead with some gold. 

The section of nearly 14,000 feet of folded Paleozoic 
sediments includes chiefly limestones, which after uplift 
and erosion were covered by Tertiary lavas and tuffs. 
The ores occur in zones in the limestones, as fissures in 
the igneous rocks, and along the contact. The minerals 
in the ore bodies are quartz, barite, pyrite, galena, sphal- 
erite, enargite, silver and gold minerals and their oxida- 
tion products. 

The Tintic is one of the oldest camps in the state, the ore 
having been discovered in 1869, and it was at first shipped 
as far as Baltimore and Wales. Since then mills have been 
erected at the mines. The chief towns are Eureka, Mam- 
moth, Robinson, Silver City, and Diamond. 

The same type of ore occurs in Big and Little Cottonwood 
canons and Bingham Canon, the latter having been worked 
longer than those of the Tintic district. The camps lie 
southeast and southwest of Salt Lake City, and the ores 
are oxidized lead-silver ores, parallel to the bedding of 
Carboniferous limestones and the underlying quartzite. 
Galena and pyrite occur in the lower workings below 
water level. 

Coeur d'Alene, Idaho (14), lying in the northern part of 
the state, is one of the most prominent producers in the 



SILVER-LEAD ORES 



373 




United States, having, in the fifteen years preceding 1902, 
produced about 160,000,000 worth of lead and silver. 

The formations of the region consist of slates, sandstones, 
and quartzites, which have been bent into east and west folds, 
the accompanying metamor- 
phism having been sufficient 
to produce new minerals. 
Igneous intrusions are, how- 
ever, rare. The ore bodies, 
which are typical veins, con- 
taining argentiferous galena, 
associated with much siderite, 
occupy fault planes, and are 
oxidized above. The chief 
minerals are quartz, siderite, 
galena, and sphalerite. The 
workable deposits carry from 
average of the district being 
per ton silver. 

Montana and Nevada, etc. — Montana contains several 
lead-silver ore localities. Those of Neihart (IT) occur as 
veins in gneiss and igneous rocks, the ores being galena, 
silver sulphides, and some blende. The veins are best de- 
fined in the gneiss, and are mostly replacement deposits, 
which have been subsequently fractured and secondarily 
enriched. Lead-silver ores also occur at Glendale and in 
Jefferson County. Some are also known in South Dakota 
and New Mexico (3). 

The Eureka district (10) of eastern Nevada, discovered in 
1868, is chiefly of historic importance. The ores are oxidized 
lead-silver ores, carrying some gold. They occur in Cambrian 



Fig. 88. — Section of lead-silver vein, 
Coeur d'Alene, Ido. (1) Country 
rock. (2) Sheared rock. (3) Galena 
and siderite. (4) Fissure with fine- 
grained galena. (5) Barren, silicified 
country rock. After Finlay, Amer. 
Inst. Min. Engrs., Trans. XXXIII: 
249. 

5 to 25 per cent lead, the 
10 per cent and 7 ounces 



374 ECONOMIC GEOLOGY OF THE UNITED STATES 

limestone which is much faulted and crushed, and is part of 
a Paleozoic section 30,000 feet thick. 

The ore is associated with a great fault, and is oxidized to 
a depth of 1000 feet. There are two mining districts, Pros- 
pect Hill and Ruby Hill. Near the mines are great por- 
phyry masses which are supposed to have afforded the ores. 
Up to 1882 the output was not far from $60,000,000 of pre- 
cious metals and 225,000 tons of lead. 

REFERENCES ON LEAD-SILVER ORES 

1. Blow, Amer. Inst. Min. Engrs., Trans. XVIII : 145, 1889. 2. Boutwell, 
U. S. Geol. Surv., Bull. 213 : 31, 1903 ; 225 : 141, 1904 ; 260 : 140, 1905. 
(Park City, Utah.) 3. Clark, Amer. Inst. Min. Engrs., Trans. XXIV : 
155. (Lake Valley, New Mex.) 4. Cross and Spencer, U. S. Geol. 
Surv., 21st Ann. Rept., II: 15, 1900. (Rico Mts., Colo.) 5. Curtis, 
U. S. Geol. Surv., Mon. VII, 1884. (Eureka, Nev.) 6. Eldridge, 
U. S. Geol. Surv., 16th Ann. Rept., II : 264, 1895. 7. Emmons, U. S. 
Geol. Surv., Mon. XII, 1886. (Leadville, Colo. A new report is in 
preparation.) 8. Emmons, U. S. Geol. Surv., Ten Mile Atlas Folio. 
(Ten Mile district, Colo.) 9. Farish, Colo. Sci. Soc, Proc. IV: 151. 
(Rico.) 10. Hague, U. S. Geol. Surv., Mon. XX, 1892. (Eureka, 
Nev.) 10 a. Kedzie, Amer. Inst. Min. Engrs., Trans. XV : 570, 1886. 
(Red Mt.) 11. Olcott, Eng. and Min. Jour. XLIII: 417, 436, 1887, 
and LIII: 545, 1892. (Eagle Co., Colo.) 12. Rickard, Amer. Inst. 
Min. Engrs., Trans. XXVI : 906, 1896. (Enterprise mine, Rico, Colo.) 

13. Ransome, U. S. Geol. Surv., 22d Ann. Rept., II: 229, 1902. 

14. Ransome, U. S. Geol. Surv., Bull. 260: 274, 1905. (Coeur 
d'Alene.) 15. Spurr, U. S. Geol. Surv., Mon. XXXI, 1898. (Aspen, 
Colo.) 16. Tower and Smith, U. S. Geol. Surv., 19th Ann. Rept., 
Ill : 601, 1899. (Tintic district, Utah.) 17. Weed, U. S. Geol. Surv., 
20th Ann. Rept., Ill : 271, 1900. 



CHAPTER XIX 
ALUMINUM 

Ores. — This is one of the few metals whose ores do not 
present a metallic appearance. Many different minerals con- 
tain aluminum, but it can be profitably extracted from only 
a few. Common clay, for example, presents an inexhaustible 
supply, but the chemical combination of the aluminum in it 
is such that its extraction up to the present time has not been 
found practicable. 

The ores of aluminum, together with the percentage of 
the metal which they contain, are : corundum, A1 2 3 
(53.3 per cent); cryolite, A1F 3 , 3 NaF (12.8 per cent); 
bauxite, A1 2 3 , 2H 2 (34.94 per cent); gibbsite, A1 2 3 , 
3 H 2 (34.6 per cent). Of these, corundum is too valuable 
as an abrasive, 'and is not found in sufficient quantity to 
permit its use as an ore of aluminum. Until the discovery 
of bauxite, cryolite was the chief source of the metal, all of 
it being obtained from Greenland (8). 

Bauxite derives its name from Baux in southern France, 
where it was first discovered, but in recent years large de- 
posits have been found in the United States. It is usually 
pisolitic in structure, and may sometimes resemble clay in 
appearance. The common impurities are silica, iron oxide, 
and titanic acid ; and the variation in the amount of these 
ingredients can be seen from the following analyses of both 
domestic and foreign occurrences : — 

375 



376 ECONOMIC GEOLOGY OF THE UNITED STATES 

Analyses of Bauxite 



Alumina (A1 2 3 ) . . 
Ferric oxide (Fe 2 3 ) . 
Silica (Si0 2 ) .... 
Lime carbonate (CaC0 3 ) 
Titanic acid (Ti0 2 ) . . 
Water (H 2 0) .... 

Moisture 

Alkalies (Na 2 0, K 2 0) . 



57.60 
25.30 

2.80 
.40 

3.10 
10.80 



61.89 
1.96 
6.01 



27.82 



3 



63.16 

23.55 

4.15 



59.22 
3.16 
3.30 

3.62 

28.80 
1.90 



61.00 
2.20 
2.10 



31.58 
3.12 



62.05 
1.66 
2.00 



30.31 
3.50 



1. Baux, France. 2. Glenravel, Ireland. 3. Wochein, Germany. 
4. Georgia. 5. Rock Run, Alabama. 6. Arkansas. 

distribution of Bauxite in the United States. — Bauxite in 
commercial quantity is known to occur in but three districts 
in the United States. These are the Georgia- Alabama dis- 
trict, the Arkansas district, and a small area in southwestern 
New Mexico. The New Mexico deposits are of little com- 
mercial importance on account of their inaccessibility. 

Georgia- Alabama (4, 6, 7). — The bauxite deposits of these 
two states form a belt about 60 miles long extending from 
Jacksonville, Alabama, to Cartersville, Georgia. The ore, 
which is either pisolitic or claylike in its character, forms 
pockets or lenses of variable diameter and depth, in the re- 
sidual clay derived from the Knox dolomite. A pronounced 
feature is their occurrence close to 900 feet above sea level, 
few being found above 950 feet or below 850 (4). 

The bauxite is believed by Hayes (4) to be a hot spring 
deposit. It is underlain by the Knox dolomite and this in 
turn by the Connasauga shales which are several thousand 
feet in thickness, and contain from 15 to 20 per cent of alu- 
mina, and also pyrite. The region is one of marked faulting. 



Plate XXV 




Fig. 1. — View of Bauxite bank, Kock Run, Ala. 11. Kits, photo. 




Fig. 2. — Furnace for roasting mercury ore, Terlingua, Tex. W. 11. Turner, photo. 



ALUMINUM 377 

Alteration of the pyrite by percolating meteoric waters has 
yielded sulphuric acid, which attacked the alumina of the 
shale, with the formation of alum and also ferrous sulphate. 
Both of these have been carried toward the surface by spring 
waters, but since they had to pass through the higher lying 



AV<-: 



-#r^ . V/,' -?' 




HE 



Fig. 89. — Geologic map of Alabama-Georgia bauxite region. After Hayes, 
U. S. Geol. Surv., Wth Ann. Rept., Ill: 552. 

limestones, the lime carbonate acted on the dissolved alum 
according to the following equation : 1 — 

A1 2 (S0 4 ) 3 + 3 CaC0 8 = A1 2 3 + 3 CaS0 4 + 3 C0 2 . 
The alumina thus formed was a light, gelatinous precipi- 
tate, which was carried upward into spring basins on the 
surface, where it finally settled. The pisolitic structure is 
thought to have been caused by the balling together of the 
gelatinous mass by currents. 

1 For clearness, the water combined with the alumina is left out. 



378 



ECONOMIC GEOLOGY OF THE UNITED STATES 



The Georgia- Alabama deposits, which represent a unique 
type of occurrence, were discovered in 1887, and have been 
worked steadily since that time. There have been some mis- 
givings regarding the exhaustibility of the domestic supply, 
but the discovery and development of the next described 
district have allayed these fears. 

Arkansas (2,3). — The occurrence of bauxite in Arkansas 
has been known since 1891, but owing to a more accessible 
eastern supply, there was little development in that region 
until 1900. The deposits, which are much more extensive 
than the Georgia- Alabama ones, are confined to a small area 




Fig. 90. — Section of Bauxite deposit, (a) Residual mantle ; (b) Red sandy clay- 
soil; (c) Pisolitic ore; (d) Bauxite with clay; (e) Clay with bauxite; 
(/) Talus; (g) Mottled clay; (h) Drainage ditch. After Hayes. 

in Pulaski and Saline counties, north and southwest of Little 
Rock. They have an average thickness of 10 to 15 feet and 
show two distinct types. In the southwesterly or Bryant 
district the lower beds show a granitic structure and rest 
directly on a mass of kaolin derived from the elseolite- 
syenite, and it is probable that the bauxite has also been 
derived directly from this rock. The upper beds are piso- 
litic and similar in character to the Georgia- Alabama ones. 
In the Fourche Mountain area only the pisolitic form is 
found. The granitic type is the purest and corresponds in 
composition to the formula of gibbsite rather than bauxite, 
while the white bauxitic kaolins run high in silica. 



ALUMINUM 379 

The origin of the Arkansas bauxites is somewhat obscure, 
but Hayes (3) considers that subsequent to the intrusion of 
the syenite into the palaeozoics of that region, the former 
was exposed by erosion of the latter. This was followed by 
a submergence of the surface below a body of salt or highly 
alkaline waters, which in some way penetrated the still 
partially hot syenite, and dissolved its minerals. On re- 
turning to the surface they attacked the syenite there, 
removing silica and alkalies and depositing alumina in its 
place. Much of the alumina was also deposited from these 
waters as a gelatinous precipitate on the ocean bottom, over 
the syenite surface. Some was also deposited with the 
Tertiary sediments then forming. 

New Mexico (1). — The bauxite deposits which occur near 
Silver City appear to have been derived from a basic volcanic 
rock, by decomposition and alteration in place. 

Uses of Aluminum, — The chief use of this metal is for 
making wire for the transmission of electric currents, but a 
large quantity of it is also used in the manufacture of articles 
for domestic or culinary use, instruments, boats, and other 
articles where lightness is wanted. It is also employed in 
the manufacture of special alloys, among which may be men- 
tioned magnalium, an alloy of aluminum and magnesium; 
and wolframinium, a tungsten-aluminum alloy. One alloy 
of this type known as partinium is said to have a ten- 
sile strength of over 49,000 pounds per square inch; Mc- 
Adamite, an alloy of aluminum, zinc, and copper, is said 
to possess a tensile strength exceeding 44,000 pounds per 
square inch; aluminum silver is an alloy of copper, nickel, 
zinc, and aluminum ; aluminum zinc includes a series of 



380 



ECONOMIC GEOLOGY OF THE UNITED STATES 



alloys containing various proportions of these two metals. 
Of growing importance is the use of aluminum for litho- 
graphic work as a substitute for stone or zinc. Another 
extending application is that of powdered aluminum for 
the production of intense heat by combustion, and in this 
connection it is used for welding tramway rails, or for the 
reduction of rare metals from their oxides. Aluminum has 
also been tried for the manufacture of grindstones and whet- 
stones, for which purpose it is said to be peculiarly suited 
owing to the property it has for forming under whetting 
action a very fine mass which adheres strongly to steel. A 
small amount of aluminum added to steel prevents air holes 
and cracks in casting. 

Uses of Bauxite. — Aside from being used for the manu- 
facture of aluminum and alum, bauxite is of some value 
for the manufacture of refractory products, its heat-resisting 
qualities being very great. 

Production of Bauxite. — The production of bauxite in the 
United States has been as follows : — 

Production of Bauxite in the United States from 1889 to 1903 



Year 


Georgia 
Long Tons 


Alabama 
Long Tons 


Arkansas 
Long Tons 


Total 


Value 


1889. . . . 

1890. . . . 
1895. . . . 
1899. . . . 


728 

1844 

3756 

15,736 


13,313 
14,499 


5045 

3445 

4645 

25,713 


728 

1844 

17,069 

35,280 

23,184 
27,322 

48,087 


$2366 

6012 

44,000 

125,598 


1900 ..... 

1902. . . . 

1903. . . . 


19,739 
22,677 
22,374 


89,676 
120,366 
171,306 



ALUMINUM 



381 



The following table shows the annual consumption of 
bauxite and its value in the United States : — 

Production, Imports, Exports, and Consumption of Bauxite in 
the United States 





Total 
Production 


Imports 


Exports 


Consumption 


Year 


Quan- 
tity 
Long 
Tons 


Value 


Quan- 
tity 
Long 
Tons 


Value 


Quan- 
tity 
Long 
Tons 


Value 


Quan- 
tity 
Long 
Tons 


Value 


1901 
1902 
1903 


18,905 
27,322 
46,087 


$79,914 
121,465 
171,306 


18,313 
15,790 
14,684 


$67,107 
54,410 
49,684 


1,000 
nil 

nil 


$3,000 


36,218 
43.112 
62,976 


$144,021 
175,875 

220,990 



World's Production of Bauxite 





1900 


1901 


1902 


Country 


Quantity 

Metric 

Tons 


Value 


Quantity 

Metric 

Tons 


Value 


Quantity 

Metric 
Tons 


Value 


United 

States 
France . . 
United 

Kingdom 


23,556 
58,530 

5,873 


$89,767 
92,596 

6,750 


19,207 
76,620 

10,357 


$79,914 
124,168 

14,515 


29,785 
96,900 

9,192 


$128,206 

174,685 

13,395 


Total . 


87,959 


$189,022 


106.184 


1218,597 


135,877 


$316,286 



Prior to 1890 nearly all the bauxite consumed in the 
United States was imported from France. The French 
ore has a high iron oxide content, and very little is now 
imported, except during periods of low ocean freights. 
Most of it is purchased by Germany. 



382 



ECONOMIC GEOLOGY OF THE UNITED STATES 



Most of the bauxite used in the United States is for 
the manufacture of aluminum, but from one fourth to one 
half of the total is employed in the manufacture of chemi- 
cal salts of aluminum, and artificial corundum, known as 
alundum. The Georgia-Alabama bauxites, on account of 
their freedom from iron, are of special value for the manu- 
facture of alum. In Europe much is used as a refractory 
material for lining furnaces. 

The production of aluminum in the United States since 
1883 has been as follows : — 

Production of Aluminum in the United States 



Year 


Quantity 
Pounds 


Year 


Quantity 
Pounds 


1883 

1885 

1890 

1895 


83 

283 

61,281 

920,000 


1900 

1901 

1902 

1903 


7,150,000 
7,150,000 
7,300,000 
7,500,000 



The domestic output comes from four large plants. 
World's Production of Aluminum 





1901 


1902 


Country 


Quantity 

Metric 

Tons 


Value 


Quantity 

Metric 

Tons 


Value 


United States . . . 

France 

United Kingdom . . 
Switzerland .... 


3,244 

1,200 

560 

2,500 


$2,238,000 
560,000 

1,225,000 


3,311 

1,355 

600 

2,500 


$2,284,900 
638,830 

1,201,425 


Total 


7,504 


— 


7,766 


— 



MANGANESE 383 



REFERENCES ON ALUMINUM AND BAUXITE 

1. Blake, Amer. Inst. Min. Engrs., Trans. XXIV : 571, 1895. (N. Mex.) 
2. Branner, Jour. Geol., V: 263, 1897. (Ark.) 3. Hayes, U. S. 
Geol. Surv., 21st Ann. Kept., Ill : 435, 1901. (Ark.) 4. Hayes, 
U. S. Geol. Surv., 16th Ann. Kept., Ill: 547, 1895. (Ga.-Ala.) 
5. Laur, Amer. Inst. Min. Engrs., Trans. XXIV : 234, 1895. (The 
bauxites.) 6. Watson, Amer. Geol., XXVIII: 25, 1901. (Ga.) 
7. Watson, Ga. Geol. Surv., Bull. 11, 1904. (Ga.) 8. For cryolite, 
see Min. Indus., VI : 251, 1897. 



MANGANESE 

Ores. — While many different minerals contain this metal, 
practically the only ones of commercial value are the oxides 
and carbonates, and in this country only the former. The 
silicates are not used as a source of manganese, owing to their 
high silica percentage. 

The important ores of manganese are the following : pyro- 
lusite, the black oxide (Mn0 2 ; 63.2 per cent Mn) ; 2 J8 ^ onie - 
lane (chiefly Mn0 2 , H 2 ; K and Ba variable), one of the 
most abundant manganese ores ; braunite (Mn 2 3 ; 69.68 per 
cent Mn) ; and toad, a low-grade, earthy brown or black ore, 
with the percentage of manganese varying from 15 to 40 per 
cent. Wad is often of too low grade, due to impurities, 
to be used as an ore of manganese ; but it is sometimes em- 
ployed for paint. Rhodochrosite (MnC0 3 ), though found as 
a common gangue mineral in some western mines, does not 
serve as a source of manganese. 

The several ores of manganese are often intimately as- 
sociated, the pyrolusite generally assuming a crystalline and 
the psilomelane a massive character. Manganese oxides are 
also often intermixed with more or less oxide of iron, and 
considerable amounts of the metal are obtained from man- 



384 ECONOMIC GEOLOGY OF THE UNITED STATES 

gauiferous zinc, silver, or iron ores. Since much manga- 
nese is used in iron reduction, the last association is of 
importance. 

To be of commercial value a manganese ore should have 
at least 40 per cent metallic manganese, and should be low 
in phosphorus and silica. High-grade ores run from 50 to 
60 per cent manganese. 

The price of manganese ores in 1903 was $8.97 per long 
ton; of manganiferous iron ore, 12.69 (18-32 per cent Mn) 
and $2.40 (1-10 per cent Mn) ; of manganiferous silver ores, 
$3.63. 

Origin. — Manganese oxide deposits are usually of second- 
ary origin, having been formed by weathering processes, 
which caused the decay of the parent rock containing man- 
ganiferous silicates, and the change of these latter to oxides. 
By circulating ground water they have often been concen- 
trated in residual clays. Although iron also may have been 
present in the parent rock, and the two are sometimes de- 
posited together, still they have in many instances been 
separated from each other, due to the fact that conditions 
favorable for precipitation are not the same for both (4), 
or because the soluble compounds of manganese formed by 
weathering are sometimes more stable than corresponding 
iron compounds, and hence may be carried farther by cir- 
culating waters before they are deposited. 

Distribution of Manganese Ores in the United States. — 

Although manganese ores are widely distributed in the 
United States, only a few localities are of commercial im- 
portance. This is partly owing to the uncertainty of the 
extent of the ore deposits and partly to the high percentage 



MANGANESE 



385 




of phosphorus which many of the ores contain, together with 
their remoteness from lines of transportation. 

Eastern Area. — Manganese deposits are found in the At- 
lantic States from Vermont to Alabama, and two states in 
this belt, Georgia 
and Virginia, lead 
in the domestic 
production. The 
common mode of 
occurrence in this 
district is as nod- 
ules or lumps in 
residual clay, simi- 
lar to the limonites 
of the same area. 
In Virginia, at 
Crimora, Augusta 
County (2), the ore 

forms pockets 5 to 6 feet thick and 20 to 30 feet long in a 
bed of clay 276 feet thick. 

In northern Georgia (1, 3, 7) the ore results from the 
decay of limestone and shales, Cave Spring and Carters- 
ville being important localities. The deposits are found 
in the areas underlain by both the crystalline and Paleozoic 
rocks, but only those associated with the latter have proven 
to be of commercial importance. In this region the rocks 
consist of Cambro-Silurian limestones and quartzites, which 
have been much folded and faulted, and have then weath- 
ered down to a residual clay, which is often not less than 
100 feet thick. The ore occurs as pockets, lenticular masses, 
stringers, grains, or lumps, irregularly scattered through the 



Fig. 91. — Map showing Georgia manganese areas. 
After Watson, Amer. Inst. Min. Engrs., Trans. 
XXXIV: 209. 



386 



ECONOMIC GEOLOGY OF THE UNITED STATES 



clay and rarely forming distinct beds. None of the de- 
posits are large, though some 30 feet in length have been 
worked. More or less limonite, barite, ocher, and bauxite 
may be associated with the ore, and, indeed, complete gra- 
dations from manganese to iron ore are found, as shown 
by the following analyses : — 



Mn 
Fe 
P 



60.61 


54.94 


41.98 


15.26 


1.45 


3.62 


16.22 


39.25 


.052 


.034 


.227 


.193 



2.30 

52.02 

.24 



The better-grade ores are usually low in silica, iron, and 
phosphorus. In the Cartersville district, which is the more 




PRE-PALEOZOIC 



Fig. 92. — Section in Georgia manganese area, showing geologic relations of 
manganese, limonite, and ocher. After Watson, Amer. Inst. Min. Engrs., 
Trans. XXXIV: 219. 

important, the ore is found in residual clays derived from 
the Beaver limestone and Weisner quartzite, while in the 
Cave Spring area it occurs only in the clays overlying the 
Knox dolomite. 

Penrose (5) thought that the manganese was derived from 
the underlying Cambro-Silurian sediments, while Watson 
on the contrary believes that the crystalline rocks to the 
east and south have furnished the ore, as none is found in 
the parent rock from which the clays were derived. The 
manganese was probably taken into solution as a sulphate 
and concentrated by circulating waters of meteoric origin 
in the residual clays where now found. 



MANGANESE 



387 



The Georgia (7) deposits have been worked for a num- 
ber of years, and the manganese was formerly marketed 
chiefly in England ; but the output is now sold entirely in 
the United States. The ore, which has to be purified by 
washing and crushing, is used in part for paint and in 
part for steel manufacture. 

Arkansas. — Manganese ore is found in the region around 
Batesville (5, 6), associated with horizontally stratified lime- 
stones' and shales, ranging from Ordovician to Carbonifer- 
ous age (Fig. 93). The Cason shale, of Silurian age, 
occurring near the middle of the section (Fig. 93 5), carries 




Eesidual Clay 
^Carboniferous 



Silurian 



Ordovician 



Fig. 93. — Section in Batesville, Ark., manganese region, illustrating geological 

structure and relation of different formations to marketable and non-market- 
able ore. After Van Ingen, Sch. of M. Quart., XXII: 324. 

manganese nodules high in phosphorus, which are not 
marketable, and others are found in the pits of residual 
clay derived from it. Farther down the slopes marketable 
ore (Fig. 93 <?), which has been derived by leaching of the 
first-mentioned ore, is found occurring in residual pockets 
in the lower lying limestones, while the residual clays 
(Fig. 93 a), formed at a higher level than the Cason shale, 
are barren of manganese. 

Other United States Occurrences. — California has a num- 
ber of manganese deposits, of which some are reported to 
be of high quality (8) ; they have been used largely in 



388 ECONOMIC GEOLOGY OF THE UNITED STATES 

chlorination works for the reduction of gold ores. Man- 
ganese occurs in Triassic sandstones near Thompson, Utah, 
and the locality became a producer in 1901 (8). Much 
manganiferous iron ore and manganiferous silver ore is 
annually obtained from the Leadville district of Colorado, 
the former being used by steel works in making spiegel- 
eisen and the latter as a flux in smelters. Lake Superior 
iron ores at times carry manganese, but it usually does 
not exceed 1 per cent. 

Uses of Manganese. — One of the principal uses of man- 
ganese is in the manufacture of alloys. Of these, spiegel- 
eisen, an alloy of iron and manganese with under 20 per 
cent manganese, and ferromanganese, a similar alloy with 
over 20 per cent manganese, are important. Other alloys 
are manganese bronze, manganese and copper with or 
without iron; silver bronze, an alloy of manganese, alu- 
minum, zinc, copper, and silver; and manganese-titanium 
alloys. 

Manganese is also used as an oxidizing agent in the 
manufacture of chlorine, bromine, and disinfectants ; as a 
coloring agent in calico printing and dyeing, in the making 
of glass, pottery, brick, as well as in paints. It is also 
employed as a decolorizer in green glass. 

Production of Manganese- — Although much used in mak- 
ing glass and steel, of which latter material the United 
States is the largest manufacturer in the world, neverthe- 
less the domestic production is small. This consequently 
necessitates the importation of large quantities, which are 
obtained chiefly from Brazil. 



MANGANESE 



389 



Production and Value of Manganese Ores in the United 
States (in Long Tons) 



Year 



Production 


Value 


5,761 


$86,415 


23,258 


190,281 


25,684 


219,050 


9,547 


71,769 


11,771 


100,289 


11,995 


116,722 


7,477 


60,911 


2,825 


25,335 



1880 
1885 
1890 
1895 
1900 
1901 
1902 
1903 



Production and Value of Manganese Ores in the United 
States by States (in Long Tons) 





1901 


1902 


1903 


State 


Produc- 
tion 


Value 


Produc- 
tion 


Value 


Produc- 
tion 


Value 


Arkansas . . . 
Georgia .... 

Utah 

Virginia .... 
All others . . . 


91 
4,074 
2,500 
4,275 
1,055 


8657 
24,674 
31,250 

52,853 
7,288 


82 
3,500 

3,041 

824 


8422 
20,830 

29,444 
10,215 


500 

483 

1,801 

41 


$2,930 

2,415 

19,611 

379 


Total . . . 


11,995 


$116,722 


7,477 


$60,911 


2,825 


$25,335 



Production and Value of Different Kinds of Manganese Ores 
in the United States (in Long Tons) 





1901 


1902 


1903 


Kind of Ore 


Produc- 
tion 


Value 


Produc- 
tion 


Value 


Produc- 
tion 


Value 


Manganese ores . 
Manganiferous 

iron ores . . . 
Manganiferous 

silver ores . . 
Manganiferous 

zinc residuum 1 


11,995 
574,489 
228,187 

52,311 


$116,722 

1,475,084 

865,959 

52,311 


7,477 

901,214 

194,132 

65,246 


$60,911 

2,001,626 

908,098 

65,246 


2,825 

584,493 

179,205 

73,264 


$25,335 

1,571,750 

649,727 

73,264 


Total . . . 


866,982 


$2,510,076 


1,168,069 


$3,035,881 


839,787 


$2,320,076 



1 As this is a by-product in the treatment of zinc ores, the value given 
to it is nominal. 



390 ECONOMIC GEOLOGY OF THE UNITED STATES 

The imports of manganese ore in 1903 amounted to 
146,056 long tons, valued at 11,278,108, and came chiefly 
from Brazil, but the British East Indies, Cuba, Germany, 
and Russia also supplied some. 

REFERENCES ON MANGANESE 

1. Brewer, Ala. Ind. and Sci. Soc. Proc, VI : 72. (Ga.) 2. Hall, Amer. 
Inst. Min. Engrs., Trans. XX : 46, 1892. (Crimora, Va.) 3. Hayes, 
Amer. Inst. Min. Engrs., Trans. XXX : 403, 1901. (Ga.) 4. Pen- 
rose, Jour. Geol., 1 : 275, 1893. (Chemical relations of iron and 
manganese in sedimentary rocks.) 5. Penrose, Ark. Geol. Surv., 
Kept, for 1890, Vol. I, 1898. (Uses, ores, and deposits.) 6. Van 
Ingen, Sch. of M. Quart., XXII : 318, 1901. (Batesville, Ark.) 
7. Watson, Amer. Inst. Min. Engrs., Trans. XXXIV: 207, 1904. 
(Ga.) 8. Birkenbine, Mineral Census, 1902, Mines and Quarries. 

MERCURY 

Ores. — While mercury is sometimes found native in the 
form of quicksilver, the most common ore is cinnabar (HgS), 
which contains 86.2 per cent mercury. Native amalgam 
of mercury and silver is known, and calomel, the chloride, 
as well as other compounds, are sometimes found. 

Mode of Occurrence. — Mercury ores are not confined to 
any particular formation, but are found in rocks ranging 
from the Ordovician to Recent Age in different parts of 
the world. Nor are they peculiar to any special type of 
rock, although igneous rocks are often found in the vicinity 
of them. They occur as veins, disseminations, or as masses 
of irregular form. Silica, either crystalline or opaline, and 
calcite are common gangue minerals, while pyrite or mar- 
casite are rarely wanting, and bitumen is widespread. 

Distribution in the United States. — California has always 
been the most important, and, in fact, at times, the only 



MERCURY 



391 



9 Quicksilver 



producing state. Deposits are, however, also known in 
Texas, Oregon, Utah, Nevada, and New Mexico. 

California (1,2,7). — The California ores occur chiefly 
in metamorphosed Cretaceous or Jurassic rocks, with some 
in the Miocene and even 
Quaternary. The depos- 
its, which are termed 
" chambered veins " by 
Becker, are fissured zones. 
Eruptive rocks seem in 
many cases to be involved 
in the ore formation, and 
at New Almaden a rhyo- 
lite dike runs parallel with 
the ore body. The ore 
here occurs along the con- 
tact between serpentine 
and shale, filling in part 
the interstices of a brec- 
cia. These mines, which are the largest in the state, have 
been worked to a depth of over 2500 feet. 

Other occurrences are in Colusa County, where the cin- 
nabar is found in altered serpentine, and in Xapa County, 
where it occurs along the contact of sandstone and slate. 
The minerals associated with these are bitumen, free sul- 
phur, stibnite, mispickel, gold and silver, chalcopyrite, py- 
rite, millerite, quartz, calcite, barite, and borax. At New 
Idria the ore is the same, but the wall rock is metamor- 
phic sandstones and shales. A third important mine is 
the Sulphur Bank, which is of very recent date. The 
vein is a fissure filled with brecciated fragments, and cuts 




Fig. 94. 



Map of California mercury local- 
ities. 



392 



ECONOMIC GEOLOGY OF THE UNITED STATES 



through sandstone, shale, and augite andesite, the cinnabar 
cementing the breccia together, but at times also impreg- 
nating the walls. Hot waters which circulate through the 
vein still deposit gelatinous silica. 

At Steamboat Springs the waters carry gold, sulphide 
of arsenic, antimony, and mercury, sulphides or sulphates 
of silver, lead, copper, zinc, iron oxide, and possibly other 
metals. They also contain sodium carbonate, sodium chlo- 
ride, sulphur, and borax. 

Cinnabar is known in Lane and Douglas counties, Oregon. 

Texas (3, 4, 5). — The Terlingua district of Brewster 

County, Texas, has caused much interest in recent years. 

The ore bodies thus far known lie in a belt 15 miles east 

and west by 4 miles 
t «^n wide, with Fresno 
Canon on the west- 
ern boundary, but 
the remoteness from 
the railroad (90 
miles) and the lack 
of water form seri- 
ous obstacles to the 
rapid development 
of this district. The 
rocks are Cretaceous 
limestone, which 
have been broken by 
several large northwest-southeast faults, with minor parallel 
ones between. Overlying these are younger sediments and 
volcanics. Only one. of the ore bodies is close to an intru- 
sive contact. 




Fig. 95. — Map showing Texas mercury region. 
After Hill, Eng. and Min. Jour., LXXIV: 305. 



MERCURY 



393 




Fig. 96. — Section of cinnabar vein in 
limestone, Terlingua, Tex. After 
Phillips, Univ. Tex. Min. Surv., 
Bull. 4:32. 



Cinnabar is the commonest ore, but other mercury min- 
erals are present, including quicksilver, which is usually 
intimately associated with calcite. Hematite and limonite 
are very common accessories, 
but pyrite is rare. The ore is 
most frequently found in fis- 
sure veins with calcite gangue, 
these fissures forming two 
series at right angles to each 
.other, of which the northeast- 
southwest ones are productive. 
The ore also occurs in brec- 
ciated strips, or as lateral extension veins. The workings 
are all shallow. Recently an extension of this area has been 
found in the Chisos Mountains near Terlingua. 

Origin. — The origin of mercury ores has been studied 
chiefly by Becker (1) and later by Schrauf (6). The for- 
mer points out that silica (either crystalline or amorphous) 
and calcite are common gangue minerals, but pyrite or 
marcasite are almost equally abundant, as is also bitumen. 
In addition to these, the ores show an irregular association 
with other metallic minerals, such as antimony, silver, lead, 
copper, arsenic, zinc, or even gold. Becker believes that 
the cinnabar has been precipitated from ascending waters 
by bituminous matter, having come up in solution as a 
double sulphide with alkaline sulphides. He further sug- 
gests that the deposits represent impregnations and are 
not replacements. 

Uses of Mercury. — The most important use of quick- 
silver is in the extraction of gold and silver by the process 



394 



ECONOMIC GEOLOGY OF THE UNITED STATES 



of amalgamation (see Gold and Silver). Its power of form- 
ing amalgams with other metals makes it of value in the 
arts for the preparation of a substance used for silver- 
ing mirrors and for other purposes. Because it is liquid 
at ordinary temperatures it can be employed in the manufac- 
ture of thermometers ; and this fact, added to its weight, 
renders it of special value in the construction of mercurial 
barometers. In medicine mercury is used in various forms, 
chiefly as calomel, while cinnabar and other compounds of 
mercury are valuable in the manufacture of pigments. For 
this purpose it was used by the American Indians and by 
the other early races of people. 

Extraction. — The mercury is usually obtained from the 
ore by the simple process of sublimation, the cinnabar 
being heated in furnaces, and the fumes of sulphur and 
metallic mercury allowed to pass off. The latter are 
caught in condensing chambers, while the former escape 
into the air. 

Production of Mercury. — California was for many years 
practically the only domestic source of mercury, but in 
1898 Texas became a producer, and will no doubt con- 
tinue so. The output of mercury is quoted in flasks of 
76^- pounds net. That of California since 1850 has been 
as follows : — 

Production of Mercury in California from 1850 to 1900 
(Flasks of 76| pounds) 



1850 7,723 

1860 10,000 

1870 30,077 



1880 59,926 

1890 ....... 22,926 

1900 . . • 26,317 



MERCURY 



395 



Production of Mercury in California and Texas from 
1901 to 1903 





1901 


1902 


1903 




Quantity 
Flasks 


Value 


Quantity 
Flasks 


Value 


Quantity 
Flasks 


Value 


Texas . . 
California 


2,932 
26,720 


$132,438 
1,285,014 


5,319 

28,974 


$239,350 

1,228,498 


5,029 
30,526 


$211,218 
1,330,916 



The imports of mercury in 1903 were valued at $1065, 
and the exports at 1446,845. 

The world's production for 1902 was as follows : — 



Country 



Quantity 
Metric Tons 



Value 



United States 
Austria . . , 
Italy . . . , 
Spain . . . 



1,190 
511 
260 

1,425 



$1,467,848 

568,929 

310,080 

1,941,387 



REFERENCES ON MERCURY 

Becker, Geology of Quicksilver Deposits of Pacific Slope, U. S. Geol. 
Surv., Mon. XIII, 1888. 2. Becker, U. S. Geol. Surv., Min. Res., 
1892: 139, 1893. (Origin.) 3. Blake, W. P., Amer. Inst. Min. 
Engrs., Trans. XXV : 68, 1896. (Cinnabar in Texas.) 4. Hill, Eng. 
and Min. Jour., LXXIV : 305, 1902. (Tex.) 5. Phillips, Univ. Tex. 
Min. Surv., Bull. 4, 1902. (Terlingua district, Texas.) 6. Schrauf, 
Zeitsch. prak. Geologie, II : 10, 1894. (Origin.) 7. Watts, W. L., 
Cal. State Min. Bur., XI : 239, 1893. (Lake County, California.) 



CHAPTER XX 



ANTIMONY 



Ores. — Stibnite (Sb 2 S 3 ) is the most important ore of 
antimony, and the metal is rarely obtained from any other 
mineral, although native antimony has been sparingly 
found. The oxide senarmontite (Sb 2 3 ) seldom occurs in 
any quantity. A small amount of antimony is present in 
some silver-lead ores. The stibnite, together with a gangue 
of quartz, and sometimes calcite, usually forms veins cutting 
igneous, sedimentary, or metamorphic rocks. 



Distribution of Antimony in United States. — Antimony 
has been found at a number of localities in the Cordilleran 
region, but the great distance of the deposits from the rail- 
road, together with the fact that the smelting plants are 
located in the East, make them of little commercial value, 
and no domestic production has been reported since 1901. 
Moreover, the large output of antimony ores and metal 
abroad, combined with low ocean freights and the absence 
of any import tax on crude antimony, are of themselves 
discouraging to domestic competition. 

The large amount of antimony now manufactured in 
the United States is obtained : (1) as a by-product from 
the smelting of foreign and domestic lead-silver ores con- 
taining small quantities of antimony ; (2) antimony regu- 
lus, or metal from foreign countries ; (3) foreign ore. 

396 



ANTIMONY 



397 



Uses. — Antimony metal is used chiefly in the manufac- 
ture of alloys of lead, tin, zinc, etc. Type metal, which is 
an alloy of lead, antimony, and bismuth, has the property 
of expanding at the moment of solidification. Britannia 
metal is tin with 10 to 16 per cent antimony and 3 per 
cent copper. Babbitt, or antifriction, metal consists of 
antimony and tin, with small amounts of lead, copper, bis- 
muth, zinc, and nickel. Tartar emetic, a potassium-anti- 
mony tartrate, is used in medicine and as a mordant for 
dyeing, while antimony persulphide is employed for vulcan- 
izing and coloring rubber. 

Production of Antimony. — The production of metallic 
antimony from domestic and foreign ores since 1890 was 
as follows : — 

Production of Antimony from Domestic and Foreign Ores 



Year 


Quantity 
Short Tons 


Value 


Year 


Quantity 
Short Tons 


Value 


1890 
1895 
1900 


938 
2013 
4226 


$175,508 
304,169 
837,896 


1901 

1902 
1903 


2639 
3561 
3128 


$539,902 
634,506 

548,433 





The production in 1903 was about three fifths of the 
entire consumption. The hard lead (antimonial lead) 
produced in the United States in 1903, as a by-product 
from impure lead-silver ores, was 21,237,440 pounds, con- 
taining 24 per cent antimony. 



REFERENCES ON ANTIMONY 

1. Blake, U. S. Geol. Surv., Min. Res., 1883-4 : 641, 1885. 2. Comstock, 
Ark. Geol. Surv., Ann. Kept, for 1888, I: 136. (Ark.) 3. Min. 
Indus., 2 : 13, 1894. (General.) 



398 ECONOMIC GEOLOGY OF THE UNITED STATES 

ARSENIC 

Although arsenic-bearing minerals are widely distributed 
in many countries, the commercially valuable occurrences 
are few. 

Arsenopyrite (FeAsS), called also mispickel and arsenical 
pyrites, is the main source of the metal. Realgar (As 2 S 2 ) 
and orpiment (As 2 S 3 ) may also serve as ores. 

Arsenopyrite is mined in Washington, where the mineral 
is used for making arsenious oxide, and more recently de- 
posits have been opened up in Floyd and Montgomery 
counties, Virginia. At the former locality the ore, which 
is chiefly arsenopyrite, averages about 14 per cent arsenic, 
.7 ounce gold, and 3 ounces silver per ton (2). 

Arsenopyrite is used chiefly for the manufacture of arse- 
nious oxide. It is employed in medicine, as a pigment, and 
as an alloy with lead for making shot. Arsenious oxide is 
used for making paris green, in glassware for destroying 
the iron coloration, in certain enamels, and as a fixing and 
conveying substance for aniline dyes. 

The domestic production of arsenious oxide in 1903 
amounted to 611 short tons valued at 136,691, and was all 
made at Everett, Wash. This, however, supplied only one 
quarter of the domestic demand, and large quantities were 
imported from Canada, Germany, and Spain. The imports 
of arsenic and its compounds in 1903 amounted to 8,357,661 
pounds, valued at $294,602. 

REFERENCES ON ARSENIC 

1. Min. Indus., II : 25, 1894. 2. Struthers, U. S. Geol. Surv., Min. Res., 
1903 : 326, 1904. (General.) 3. Merrill, Non-Metallic Minerals, 
30, 1904. 



CHROMIC IRON ORE 399 

BISMUTH 

Ores. — The principal ores of this metal, together with 
the percentage of metallic bismuth which they contain, are : 
Bismuthinite (Bi 2 S 3 , 81.2) ; bismite (Bi 2 3 , 96.6) ; and bis- 
mutite (Bi 2 3 , C0 2 , H 2 0, 80.6). Although all of these 
contain a high percentage of metallic bismuth, the content 
of the ore as mined does not usually exceed ten or fifteen 
per cent. Bismuth ores are commonly associated with those 
of gold and silver, and the metal is obtained as a by-product 
in the smelting of these. 

Distribution. — There are many scattered occurrences of 
bismuth ores throughout the Rocky Mountain states, but 
Colorado is the most important, and in 1904 Leadville was 
the only producing region. 

Uses and Production. — Bismuth is chiefly valuable on 
account of the easily fusible alloys which it forms with lead, 
tin, and cadmium ; the melting point of some of these lies 
between 64° C. and 94.5° C. They are therefore employed 
in safety fuses for electrical apparatus, safety plugs for 
boilers, dental amalgams, etc. The production of bismuth 
in 1904 was 5184 pounds, valued at 1314. The imports of 
metallic bismuth in 1904 amounted to 185,905 pounds, 
valued at #339,058. 

CHROMIC IRON ORE 

Ores. — Chromite (FeO, Cr 2 3 ) is the chief source of the 
compounds of the metal chromium which are used in the arts. 
This ore occurs sometimes in alluvial deposits, but more 
commonly in basic magnesian rocks, notably serpentine. 



400 



ECONOMIC GEOLOGY OF THE UNITED STATES 



Origin of Chromite. — It has been pointed out by Pratt (4) 
that chromite occurs most commonly around the border of 
basic magnesian rocks of igneous origin. This is believed 
to indicate that the chromium existed in the original molten 
rock, and that, as this basic magma cooled, the chromite, 
being one of the earliest minerals to crystallize, separated 
out along the border of the mass because this portion was 
the first to cool. As the cooling proceeded, convection cur- 
rents within the molten mass would bring additional supplies 
to the border. 

Analyses (5). — The following table gives the composition 
of several of the types of chromic iron ores : — 







COLERAINE, 












France 


Can. 

Concentrated 

Product 


Asia 
Minor 


Styria 


Calif. 


Russia 


Cr 2 3 


37.00 


53.64 


53.00 


53.00 


42.20 


59.00 


Si0 2 


2.53 


2.31 


2.15 


2.50 


5.48 


2.20 


A1A 


13.15 


14.02 


7.62 


8.00 


13.60 


10.00 


MgO 


12.53 


15.75 


12.31 


11.58 


14.88 


11.62 


FeO 


34.79 


11.47 


24.92 


24.92 


23.84 


18.18 


CaO 




2.81 











The price of chromic iron ore is based on its percentage of chromic 
oxide, the standard ore containing 50 per cent. Every unit above this 
is valued at from 75 cents to $1 per ton; but when the percentage is 
below 50 per cent, the value decreases at an even greater rate. How- 
ever, ores carrying only 45 per cent of chromic oxide are easily market- 
able. Low silica is desirable. 



Distribution in the United States. — In the United States 
chromite was for a time obtained from Chester and Delaware 
counties, Pennsylvania, and Baltimore County, Maryland, 



CHROMIC IRON ORE 401 

and the exhaustion of these deposits was followed by the 
opening of others in San Luis Obispo County, California. 
Subsequently the importation of Turkish and Russian chro- 
mite commenced, followed by additional supplies from 
Canada and Newfoundland. This foreign chrome iron ore, 
especially the Turkish, can be placed on the American 
market so cheaply that there has been little development of 
our own deposits. The importation of chromic iron ore 
from New Caledonia is also increasing. 

Chromite occurs in a number of places in California besides the one 
referred to above; and also in North Carolina, in a belt of peridotite rock 
extending from Ashe County to Clay County. In this area, however, the 
chromite has been found in quantity at only a few localities (3). 

Uses. — Metallic chromium has no direct use; but raw 
chromite and chromium salts have a variety of applications. 
Owing to its great heat-resisting qualities, chromite is 
employed in the manufacture of refractory bricks. Such 
bricks are sometimes used for lining basic open-hearth fur- 
naces, and as a hearth lining for water-jacket furnaces in 
copper smelting. They stand rapid changes of temperature 
well, and are not attacked by molten metals. 

In the presence of carbon, chromium makes steel extremely 
hard and resistant to shocks ; therefore chrome steel is 
suited to a variety of uses, as in the manufacture of paper, 
hard-edged tools, etc. An alloy of iron and chromium is 
used in armor plates, alloys of ferro-chromium and ferro- 
nickel being added to the molten steel before casting. Most 
of the chromite mined is used for pigments because of the 
red, yellow, and green color of its compounds, chromate and 
bichromate of potash. In these forms the substance is em- 

2d 



402 



ECONOMIC GEOLOGY OF THE UNITED STATES 



ployed in dyeing, calico printing, and the making of pig- 
ments useful in painting, printing wall papers, and coloring 
pottery. Alkaline bichromates are employed for tanning 
skins, and some chromium salts have a medicinal value. 

Production of Chromite. — The amount of chromite pro- 
duced in the United States is small, and in 1903 California 
was the only source of supply. The production for several 
years was as follows : — 

Production of Chromite in the United States from 1900 to 1903 



Year 


Quantity 
Long Tons 


Value 


1900 

1901 

1902 

1903 


140 
368 
315 
150 


$1400 
5790 
4567 
2250 



The value of the imports for the last three years was : — 



Year 


Chromate and 

Bichromate 

of Potash 


Chromic 
Acid 


Chrome 
Ore 


Total 


1901 

1902 , 

1903 


$29,224 
32,174 


$10,861 
11,115 


$363,108 
582,597 
292,025 


$403,193 
593,712 
324,199 



REFERENCES ON CHROMIC IRON ORE 

1. Glenn, Amer. Inst, of Min. Engrs., Trans. XXXI : 374, 1902. 2. May- 
nard, ibid., XXVII : 283, 1898. (Newfoundland.) 3. Pratt, U. S. 
Geol. Surv., Mineral Resources, 1901: 941, 1902. (General.) 
4. Pratt, U. S. Geol. Surv., Bull. 180. (Origin.) 5. Anon., Min. 
Indus., VI : 147, 1898. (Analyses.) 



NICKEL AND COBALT 403 

MOLYBDENUM 

Ores and Occurrences. — Molybdenite (MoS 2 ) and, less com- 
monly, wulfenite (PbMo0 4 ), are the chief sources of this 
metal. 

Molybdenite forms irregular masses or disseminations in 
crystalline rocks, and many occurrences are known in the 
West, for example, in California, Washington, Montana, Utah, 
Arizona, New Mexico, and in the East, in Maine. An ore to 
be marketable must contain over 45 per cent of molybdenum 
and be free from copper, the average price of a 50 to 55 per 
cent ore being about $400 per ton. 

Uses. — Its chief use is in the manufacture of chemicals, 
especially ammonium molybclate, and for coloring porcelain 
green. A nickel-molybdenum alloy is also made. The use 
of molybdenum for hardening steel is increasing, it being 
used chiefly for tool steel. 

Production of Molybdenum. — The production of molyb- 
denite in 1903 was 6200 tons crude ore, but very little of 
this was concentrated and marketed. 

REFERENCES ON MOLYBDENUM 

1. Crooks, Bull. Geol. Soc. Amer., XV: 283, 1904. (N.Y.) 2. Pratt, 
U. S. Geol. Surv., Min. Res., 1903 : 307, 1904. (General.) 3. Smith, 
U. S. Geol. Surv., Bull. 260 : 197, 1905. (E. Me.) 

NICKEL AND COBALT 

Ores. — These two metals can best be treated together, for 
nearly all the ores containing one are apt to carry some of the 
other, and furthermore, in smelting, the two metals go into 
the same matte, and are separated later in the refining process. 



404 



ECONOMIC GEOLOGY OF THE UNITED STATES 



The ores of nickel and cobalt, together with their composi- 
tion and the percentage of nickel or cobalt they contain, are : 



Ore 


Composition 


Ni 


Co 


Pyrrhotite (nickeliferous) 

Millerite 

Pentlandite 

Genthite 

Niccolite 

Linnseite 


Fe n S 12 

MS 

(FeNi)S 

2 Ni0 2 , 2 MgO, 3 Si0 2 , 6 H 2 

NiAs 
(CoNi) 3 S 4 


0-6 
64.6 
22 

22.46 
43.9 
30.53 


21.34 



The nickeliferous pyrrhotite is the most widely distributed 
of the nickel ores, and may carry small amounts of cobalt. 
It is also called magnetic pyrites. The percentage of nickel 
ranges from a trace to 6 per cent, but an increase above this 
brings it into pentlandite. The millerite is sometimes found 
associated with pyrrhotite ores. Of the genthite, the variety 
known as garnierite forms the ores, and carries from 21 to 45 
per cent nickel oxide. 

Distribution. — Very little direct mining for nickel and 
cobalt is done in the United States, but at Mine la Motte, 
Missouri, considerable quantities have been obtained annually 
as a by-product in lead mining. (See under Lead.) 

Eastern Occurrences of Nickel. — The Gap Nickel Mine, 
Lancaster County, Pennsylvania, is the most important 
eastern occurrence. It was actively worked from 1863 to 
1880, being during that period the only nickel ore mined 
on this continent. In 1902 the mine was again operated. 
The ore is pyrrhotite associated with amphibolite, an altered 
intrusive, the whole inclosed by mica-schist. The pyrrhotite 
is believed to have originated by magmatic segregation (4). 



NICKEL AND COBALT 405 

Nickel minerals have also been found in the basic magnesian 
rocks of North Carolina. 

Western Occurrences. — Deposits of nickel and cobalt ores are 
known in Idaho and Oregon, but they have not yet assumed 
importance. Nickel ore is found in Ferry County, Wash- 
ington, and other deposits are reported from Sheridan and 
Piney Creek, Wyoming, as well as at several localities in 
Nevada, Idaho, Arizona, and South Dakota ; but none of the 
occurrences are worked, and the main source of supply on 
this continent comes from Sudbury, Ontario (1, 2). 

There, the ore, which occurs in enormous masses, is a nickeliferous 
pyrrhotite, and the output forms probably one half of the world's produc- 
tion. The ore occurs on the contact of quartzite and diorite, or forms, 
more often, scattered irregular masses in the latter. Its origin has been 
a matter of some dispute, some having regarded it as a product of mag- 
matic segregation, while others believe the ore to have been deposited in 
the crushed diorite. A partial analysis shows : Cu, 8.05 ; Ni, 2.97 ; Fe, 
26.21; Si0 2 , 26.05; S, 19.08. 

The second important source of the world's nickel ore is the mines of 
New Caledonia, in the Pacific Ocean, off the east coast of Australia. The 
ore is garnierite. 

Uses of Nickel. — The most important and increasing use of 
nickel is for the manufacture of nickel and nickel-chromium 
steel. This, on account of its great hardness, strength, and 
elasticity, is used for making armor plate, gun shields, turrets, 
ammunition hoists, etc. Krupp steel, which may be taken 
as a type, has approximately 3.5 per cent nickel, 1.5 per cent 
chromium, and .25 per cent carbon. Owing to its abrasive 
resistance, nickel-steel is now much used for rails. Other 
important uses are for large forgings, marine engines, wire 
cables, and electrical apparatus. A steel with 25 to 30 per 
cent nickel shows high resistance to corrosion by salt, fresh 



406 



ECONOMIC GEOLOGY OF THE UNITED STATES 



or acid waters, or by superheated steam. German silver is 
an alloy of zinc, copper, and nickel. 

Uses of Cobalt. — Cobalt steel, while having a high elastic 
limit and breaking strength, cannot compete with nickel steel 
on account of its high cost, and the main use for cobalt is as 
a pigment. 

Production. — The production of nickel from domestic ores 
and cobalt oxide in the United States from 1892 to 1901 was : 

Production of Nickel and Cobalt from Domestic Ores 





Nickel 


Cobalt Oxide 


Year 


Quantity- 
Pounds 


Value 


Quantity- 
Pounds 


1892 

1895 

1900 

1901 

1902 

1903 


92,252 

10,302 

9,715 

6,700 

5,748 

114,200 


$50,739 
3,091 
3,886 
3,551 
2,701 
45,900 


7,869 
14,458 

6,471 
13,360 

3,730 
120,000 



The amount of nickel produced in Canada in 1903 was 
12,505,510 pounds. The imports of cobalt oxide in 1903 were 
73,350 pounds, valued at 1145,264, while the total value of 
the nickel imported in the same year was 11,849,620. The 
exports of nickel oxide and matte in 1901 were $1,483,889. 

The World's Production of Nickel 





Quantity 


Value 


Canada, 1903 

France, 1902 . 

Germany, 1902 


12,505,510 pounds 
1,600 met. tons 
1,605 met. tons 


$5,002,204 
1,080,800 
1,122,271 





PLATINUM GROUP OF METALS 407 

REFERENCES ON NICKEL AND COBALT 

1. Barlow, Can. Geol. Surv., Ann. Kept., XIV, pt. H, 1904. (Ontario.) 
2. Dickson, Amer. Inst. Min. Engrs., Trans. XXXIV: 3, 1904. 
(Ontario.) 3. Hodges, Amer. Inst. Min. Engrs., Trans. X : 657, 1882. 
(Nev.) 4. Kemp, Amer. Inst. Min. Engrs., Trans. XXIV : 620, 1895. 
(Pa.) 5. Neill, Amer. Inst. Min. Engrs., Trans. XIII : 634, 1885. 
(Mo.) 

PLATINUM GROUP OF METALS 

Platinum. — The ores of platinum are native platinum 
(100 per cent Pt), and sperrylite, PtAS 2 (56.5 per cent 
Pt). The former is commonly found in placer deposits, but 
it has also been noted in basic igneous rocks rich in olivine, 
such as peridotite, or in serpentine derived from it. The 
sperrylite never occurs in large quantities, but has been 
found in association with nickel and copper ores. Iridos- 
mine and osmiridium are also known to carry platinum. 

The nuggets found in placers are commonly regarded as 
being pure native platinum, but this, according to Kemp (4), 
is only true in part, most of those assayed yielding between 
70 and 85 per cent, and the richest recorded being 86.5 per 
cent. The balance is made up largely of iron, the highest 
percentage of this noted being 19.5 per cent in a Ural 
specimen. Iridium, rhodium, and palladium are always 
present. Until the platinum falls below 60 per cent the 
iridium rarely reaches 5 per cent, rhodium 4 per cent, while 
palladium is less than 2 per cent. Other elements that have 
been detected in the nuggets are osmium, ruthenium, cop- 
per, and even gold, while chromite is a common associated 
mineral (4). 

Distribution in the United States. — The domestic supply 
of platinum, never large, has been obtained in recent years 



408 



ECONOMIC GEOLOGY OF THE UNITED STATES 



as a secondary product from gold-placer deposits in Trinity 
and Shasta counties, California, and while its occurrence has 
been reported in many other gold placers of the Northwest 
and Alaska, still none of them have proven sufficiently rich 
to work. Iridosmine and a natural alloy of iron and nickel 
called josephinite are found associated with the gold. 

In addition to the above sources, platinum is also found in 
the copper ores of the Rambler mine, Wyoming, and has 
been saved from the slimes obtained in treating the copper 
ore and matte at this locality. The covellite in the ore 
assays .06 to 1.4 ounces per ton of platinum. 

Uses. — Platinum was first used as an adulterant of gold, 
and in Russia it was used for coinage from 1828 to 1845. 
At the present time it is employed for crucibles and other 
chemical apparatus which are to be subjected to high temper- 
atures or strong acids. It is also of value in dentistry, for 
electric lamps and electric apparatus, for jewelry, and in 
photography. The price of it has risen steadily in recent 
years, so that it is as valuable as gold. 

Production. — The production in the United States from 
1880 to 1903 was as follows : — 

Production of Platinum in the United States 



Year 


Quantity 
Ounces 


Value 


Year 


Quantity 
Ounces 


Value 


1880 
1885 
1890 
1895 


100 
250 
600 
150 


1400 
187 

2,500 
900 


1900 
1901 
1902 
1903 


400 

1,408 

94 


$2,500 
27,526 

1,874 
6,080 



PLATINUM GROUP OF METALS 409 

Since the close of 1899 platinum has risen steadily in price, 
reaching a maximum of $20 per ounce in 1902. 

The imports of platinum, both crude and manufactured, 
amounted to 11,987,980 in 1902, and 82,055,933 in 1903. 
The domestic production is entirely inadequate to supply 
the demand, and the greater portion of the supply of the 
United States, and in fact the world, is obtained from the 
platinum placers of the Urals (5). 

REFERENCES ON PLATINUM 

1. Day, U. S. Geol. Surv., 19th Ann. Kept., VI : 265, 1898. 2. Day, Amer. 
Inst. Min. Engrs., Trans. XXX : 702, 1901. (N. Amer.) 3. Donald, 
Eng. and Min. Jour., LV : 81, 1893. (Can.) 4. Kemp. Min. Indus., 
X: 540, 1902; and U. S. Geol. Surv., Bull. 193, 1902. (General.) 
5. Purington, Eng. and Min. Jour., LXXVII : 720, 1904. (Russia.) 

Palladium. — This metal is found associated with platinum 
and also native and alloyed with gold (Brazil). It is of 
silver-white color, ductile and malleable, and is unaffected 
by the air. Its great rarity and consequent high value has 
restricted its use, but a small amount is used for some mathe- 
matical and surgical instruments, for compensating balance 
wheels and hair springs for watches, and for finely graduated 
scales. 

In the United States it has been reported from the platinum 
deposits of the Pacific Coast and from the Rambler mine in 
Wyoming. 

Osmium. — This, the heaviest and most infusible metal 
known, occurs alloyed with platinum and also with iridium 
in iridosmine. In the United States small quantities have 
been found in the platinum placers of California. 

Iridosmine is employed for pointing pens and fine tools, 



410 ECONOMIC GEOLOGY OF THE UNITED STATES 

while osmic acid is used for staining anatomical prepara- 
tions in microscopic work. 

Iridium. — Iridium is found chiefly in Russia and Cali- 
fornia, alloyed with platinum or osmium. It is a lustrous, 
steel-white metal of great' hardness, and is, next to osmium, 
the most refractory metal known. 

An alloy of iridium and platinum has been used for 
standard weights and measures, and iridium is also used 
in photography. 

TIN 

Ores. — Cassiterite (Sn0 2 ), with 78.6 per cent metallic tin, 
is the principal ore of this metal, but owing to the pres- 
ence of impurities the ore rarely shows this composition. 
Its hardness (6-7), imperfect cleavage, nonmagnetic charac- 
ter, high specific gravity (6.8-7.1), and brittleness help to 
distinguish it from other minerals that are liable to occur 
with it. The mineral stannite, or tin pyrites, a complex 
sulphide of copper, iron, and tin, rarely serves as an ore. 
Stream tin is the name applied to cassiterite found in 
placers. 

Mode of Occurrence. — Cassiterite of primary character is 
usually found in veins of pegmatite, or, more commonly, 
greisen (quartz and muscovite or lepidolite), around the 
edges of granite areas. This, together with the associa- 
tion of fluorite, tourmaline, and topaz with the ore, indicate 
quite clearly that it may be the result of fumarolic action. 
This type of occurrence is, however, of little commercial 
value, and over 80 per cent of the world's supply comes 
from placers whose materials have been derived from tin- 
bearing veins. 



TIN 



411 



Distribution in the United States. — Although tin has 
been found at a number of localities in the United States, 
only a very few of these can be looked upou. as commercial 
sources. 

The Black Hills (1, 2, 6) of South Dakota and Wyoming 
is perhaps the best known tin-producing region of the 
United States, 
and although 
much money has 
been sunk in 
its development 
and many ex- 
citing rumors 
have been pub- 
lished regarding 
it, the output 
has been ex- 
ceedingly small. 
Here the tin oc- 
curs either in 
pegmatite dikes 
or quartz veins and in placers. The Harney Peak deposits 
of the northern Black Hills have produced but little, but 
the Nigger Hill region of Wyoming, in the northwestern 
part of the hills, seems to be more promising. 

More recently the tin deposits of North and South Caro- 
lina (4, 6) have been attracting considerable attention. These 
lie in a belt extending from Cherokee County, South Caro- 
lina, to Lincoln County, North Carolina. The cassiterite 
occurs as an original constituent of pegmatite dikes, but 
is somewhat irregularly distributed in them. Some of the 




Fig. 97. — Sketch map showing local ion of Carolina tin 
belt. After Graton, U. S. Geol. Surv., Bull. 2G0. 



412 ECONOMIC GEOLOGY OF THE UNITED STATES 

mines now being worked at Gaffney, South Carolina, and 
Kings Mountain, North Carolina, are promising. An inter- 
esting feature is that the dikes are of undoubted igneous 
origin. 

Tin has been reported from a number of localities in 
Alaska (3), but the production is still very small, that 
during 1903 and 1904 having amounted to not more than 
100 tons. 

The most important occurrences are on the Seward pen- 
insula, where it occurs in placers, quartz-porphyry dikes, 
granites, or in sedimentaries near their contact with the 
igneous rock. In the dikes the accompanying minerals are 
tourmaline, topaz, fluorite, zinnwaldite, wolframite, quartz, 
epidote, pyrite, galena, etc. 

The amount of tin ore produced in the United States 
is entirely too small to supply the demand, and the main 
source of supply for this country, and indeed for the world, 
is the Malay peninsula, while other regions of commercial 
importance are Australia, Bolivia, and Great Britain. 

Uses of Tin. — Tin is used chiefly for the manufacture of 
bronze and tin plate, and to a smaller extent in plumbing 
as well as less important purposes. Britannia metal is com- 
posed of from 82 to 90 parts of tin alloyed with antimony, 
copper, and sometimes zinc. 

Production of Tin. — The world's production for a number 
of years has been behind the demand, a fact which has not 
only kept up the price of this metal, but also stimulated 
prospecting and mining. 

The world's production for 1904 as given by the Engineer- 
ing and Mining Journal was : — 



TITANIUM 413 

Country Tons 

Straits Settlements 65,696 

Banka and BiUiton 16,394 

Bolivia 10,304 

Australia and Tasmania 5,692 

England 4,796 

Germany and Austria 112 

Miscellaneous 140 

Total 103,134 

The price of tin on the New York market in 190-4 averaged 
about 28 cents per pound. The United States in 1904 con- 
sumed about 43,120 tons of tin. 

REFERENCES ON TIN 

1. Blake, Amer. Inst. Min. Engrs., Trans. XIII : -601. (Black Hills.) 
2. Blake, U. S. Geol. Surv., Min. Res., 1883-84 : 592, 1885. (Ores 
and deposits). 3. Collier, U. S. Geol. Surv., Bull. 220, 1904. 
(Alaska and general.) 4. Graton, U. S. Geol. Surv., Bull. 260 : 188, 
1905. (X. Ca. and S. Ca.) 5. Hess and Graton, U. S. Geol. Surv., 
Bull. 260 : 161, 1905. (Occurrence and distribution). 6. Struthers 
and Pratt, U. S. Geol. Surv., Min. Res., 1903 : 335, 1904. (U. S.) 
7. Weed, U. S. Geol. Surv., Bull. 178, 1901. (Texas.) Also 
Bull. 213 : 99, 1903. 8. Winslow, Eng. and Min. Jour., XL : 320, 
1885. (Va.) 

TITANIUM 

Ores. — Among the minerals carrying titanium the most 
abundant is ilmenite (FeO, Ti0 2 ), which occurs in many 
deposits of magnetite. Rutile (Ti0 2 , 60 per cent Ti when 
pure), though less abundant, is not uncommon. Titanium is 
also found in a number of other minerals, many of which 
are rare. 

Occurrence. — For many years Norway has been the chief 
producer of this metal ; but in 1900 large deposits of rutile 
were discovered in Virginia, from which, up to the end of 
1901, about 40,000 pounds had been extracted. 



414 ECONOMIC GEOLOGY OF THE UNITED STATES 

The Virginia ore (2), which is found in Nelson County, 
occurs in the form of small granules, disseminated through 
a ground mass of feldspar or as a segregation in quartz, in a 
rock of probable igneous origin. Until the discover} 7 of the 
Virginia deposits, the domestic demand, which has been 
small, was supplied from deposits in Chester County, 
Pennsylvania. 

Uses. — Titanium is used for producing yellow underglaze 
colors on pottery, and also in the manufacture of artificial 
teeth, to give them an ivory tint. Another use is in the 
alloy ferro-titanium. Its commercial values as a steel-hard- 
ening metal are not yet thoroughly proven, but from .5 to 3 
per cent titanium appear to materially increase the transverse 
and tensile strength of steel. By the use of the electric fur- 
nace, ferro-titanium can be produced directly from the ores, 
which would open a use for our American titaniferous 
magnetites. 

REFERENCES ON TITANIUM 

1. Merrill, Non-metallic Minerals: 109, 1904. (General.) 2. Merrill, 
Eng. and Min. Jour., LXXIII : 351, 1902. (Va.) 3. Pratt, U. S. 
Geol. Surv., Min. Res., 1903 : 309, 1904. 

TUNGSTEN 

Ores. — The ores of tungsten are wolframite ([FeMn] W0 4 ), 
hiibnerite (MnW0 4 ), and scheelite (CaW0 4 ). Of these 
wolframite is the most abundant, and scheelite, the most 
easily reducible ore of tungsten, the least abundant. Schee- 
lite is found in but few localities in the world, and in the 
United States occurs in commercial quantity at only one 
locality. Although the ores of tungsten are rare, the 
quantity available exceeds the demand. 



TUNGSTEN 415 

Occurrence. — Most of the known American deposits of 
tungsten ores are found in the western states, especially 
Arizona (1, 2, 6), Nevada, and Colorado. That found near 
Dragoon, Arizona (6), consists of hubnerite with subordinate 
scheelite, and concentrates easily to a product yielding W0 3 , 
70.22; Si0 2 , .30; Fe, 1.90; Mn, 19.82; CaO, 4.87; MgO, 
3.40. Rich ores are found in White Pine County, Nevada, 
at some distance from the railroad. In Colorado wolframite 
and hubnerite occur in several counties, and have been mined 
to some extent. Eastern occurrences are rare, but scheelite 
is found at Longhill, Connecticut (8), where it occurs along 
the contact of limestone with diorite and hornblende gneiss. 
Tungsten is also found associated with the Cambrian sili- 
ceous gold ores of the Black Hills region, South Dakota (4), 
but this source has not become of great importance. 

Uses. — Tungsten has been used for some years to fix the 
color in wash goods and make them fireproof. It has also 
been employed for manufacturing stained paper. But the 
most important present use is for the alloy ferro-tungsten, 
or in the manufacture of tungsten-steel. Alloys of tung- 
sten, aluminum, and copper are also made. The fluores- 
cent properties of tungstate of lime make it useful in the 
Rontgen ray apparatus. Tungsten is also employed for 
coloring glass. 

Production. — In 1903 the production was . 2451 short 
tons, yielding 292 short tons concentrates valued at 143,639, 
or $149 per ton. This production came from Colorado, 
Arizona, and Connecticut. 

In 1903 ferro-tungsten-chrome alloys were imported to 
the value of 118,136. 



416 ECONOMIC GEOLOGY OF THE UNITED STATES 

REFERENCES ON TUNGSTEN 

1. Blake, Eng. and Min. Jour., LXV : 608, 1898. (Ariz.) 2. Blake, Min. 
Indus., VII : 720, 1899. (Ariz.) 3. Blake, Amer. Inst. Min. Engrs., 
Trans., XXVIII : 543, 1899. 4. Irving, Amer. Inst. Min. Engrs., 
Trans., XXXI : 683, 1902. (S. Dak.) 5. Pratt, U. S. Geol. Surv., 
Min. Res., 1903: 304, 1904. (General.) 6. Rickard, Eng. and 
Min. Jour., LXXVIII : 263, 1904. (Ariz.) 7. Thomas, Min. and 
Met., XXIV : 301. (Ores and uses.) 8. Hobbs, U. S. Geol. Surv., 
22d Ann. Kept., II : 13, 1902. (Conn.) 



URANIUM AND VANADIUM 

Ores. — The minerals serving as the ores of uranium metals 
are uraninite (U0 3 , U0 2 , PbO, N, etc.), gummite (doubt- 
ful composition), and gamotite. The last-mentioned also 
carries vanadium, as does also vanadinite [(PbCl)Pb 4 (V0 4 ) 3 ]. 
The chief sources of uraninite are the mines near Central 
City and in Montrose County, Colorado. Gamotite occurs 
in Montrose County, Colorado, and also in Utah, while 
vanadinite has been found in some quantity in the gold 
and silver mining districts of Arizona and New Mexico. 

Uses. — Uranium and vanadium increase the strength and 
toughness of steel, and are used to a small extent in the 
manufacture of ferro-alloys. Uranium oxides are used for 
coloring porcelain and glass, and vanadium oxide as a 
dyeing material. Vanadium compounds are employed in 
making vanadium bronze. 

Production. — The output of the ores of these minerals 
in 1901 came chiefly from Colorado, and amounted to 375 
short tons. In 1903, as a result of much prospecting and 
developmental work, there was a production of 432 short 
tons of crude ore. Thirty tons of concentrates were sold 



URANIUM AND VANADIUM 417 

at a value of 85625. Most of the uranium and vanadium 
ores mined in the United States are exported, but a large 
quantity of uranium and vanadium salts are imported, the 
value of these in 1903 amounting to 113,498. 

REFERENCES ON URANIUM AND VANADIUM 

1. Boutwell, U. S. Geol. Surv., Bull. 260 : 200, 1905. (Utah.) 2. Pratt, 
U. S. Geol. Surv., Min. Res., 1901. 3. Merrill, Non-Metallic Min- 
erals : 299 and 320, 1904. (General.) 



2e 



INDEX 



Abrasives, 158. 
artificial, 165. 
production of, 165. 
references on, 166. 

See Buhrstones, Whetstones, Pumice, Co- 
rundum, Garnet, Quartz, Infusorial 
Earth. 
Actinolite, as gangue mineral, 295. 
Adobe clay, defined, 99. 
jEolian soils, 214. 

Alabama, bauxite, 376 ; clinton ore, 266 ; fuller's 
earth, 175 ; graphite, 179 ; kaolin, 101 ; 
limonite, 271 ; phosphate, 153 ; Port- 
land cement materials, 119 ; stoneware 
clay, 103 ; Warrior coal, analysis, 7. 
Alabaster, 143. 

Alaska, coal, 32 ; coal mining, 33 ; copper, 29S 
gold, 353 ; lignite, analysis from, 6 
magmatically segregated ores, 225 
petroleum, 54 ; tin, 412 ; yield of gold 
ores, 332. 
Albertite, properties, 59. 

distribution, 59. 
Algeria, onyx marbles, S3. 
Algonkian, copper in, 295 ; iron in, 260. 
Alkali soils, 215. 
Alkalies, effect on clay, 96. 
Alluvial soils, 214. 
Almandite, uses as gem, 194. 
Alumina, effect on clay, 95. 
in iron ores, 252. 
in soils, 214. 
Aluminum, 375. 

for lithographic work, 1S2. 
ores of, 375. 
production of, 3S2. 
references on, 383. 
uses of, 379. 
Alundum, 165. 
Amethj-st, as gem, 195. 
Amorphous phosphates, see Phosphates. 
Amygdaloids, copper-bearing, 2SS. 
Analyses of, anthracite coal, S ; asphaltites, 
60 ; bauxite, 376 ; bituminous coal, S ; 
bituminous rocks, 61 ; cement rock, 
natural, 112 ; chromite, 400 ; clays, 9S ; 
coal, elementary, 14 ; copper ores, 
Butte, 2S5; fuller's earth, 175; glass 
sand, 177; greensand, 156; gypsum, 
143; hematites, 264, 268; "kaolin, 



crude, 101 ; kaolin, washed, 101 ; lig 
nite, elementary, 14 ; limestones, 109 
limonites, 272 ; lithographic stone 
181 ; magnetites, non-titaniferous, 
257; magnetites, titaniferous, 25S 
maltha, 60 ; mine waters, 227 ; min 
eral waters, 206; monazite, 191 
natural gas, 43; peat, elementary, 
14; petroleum, 41; phosphates, 154 
Portland cement materials, 115 ; Port- 
land cements, 116; proximate, of 
United States coals, 6 ; rock salt, 
131 ; solid matter in brine, 131 ; 
waters, sea and ocean, 124. 
Analysis of, barite. 170 ; bat guano, 155 ; bitu- 
minous coal ash, 9 ; brick clay. 98 ; 
calcareous clay, 98 ; copper ore, 298 ; 
fire clay, 9S ; graphite, 17S ; gypsum, 
calcined, 144 ; kaolin, 98 ; kaolinite, 
9S ; lignite ash, 9 ; molding sand. 189 ; 
nickel ore, Canada, 405 ; oil shale, 57 ; 
peat ash, 9; pyrite, 199; shale, 98; 
stoneware clay, 98 ; tungsten concen- 
trates, 415; zinc ore, 315; zinc ore, 
Creede, Colo., 319 ; zinc ore, Lead- 
ville, 318 ; zinc ore, New Jersey, 



Anglesite, 303, 305, 371. 
Anhydrite, defined, 139. 
Anthracite, 5. 22. 

effect of igneous intrusions on, 15. 

price per ton, 34. 

properties of, 5. 
Anthraxolite, occurrence and properties, 59. 
Antimony, 396. 

distribution in United States, 396. 

gangue minerals, 396. 

mode of occurrence, 396. 

production, 397. 

references on, 397. 

sources, 396. 

uses, 397. 

with mercury, 393. 
Apatite, as a fertilizer, 147. 

sources, 147. 
Apex, 239. 
Appalachian coal field, 20. 

anthracite area, 22. 

bituminous area, 21. 

character of bituminous coals, 22. 
Appalachian petroleum, distillates from, 42. 

419 



420 



INDEX 



Appalachian region, copper ores of, 294. 
depth of oxidation in ore bodies, 244. 
petroleum in, 48. 
Apsdin, Joseph, discoverer of Portland cement, 

113. 
Aquamarine, 194. 
Archaean, iron ores in, 261. 
Argentite, 285, 325. 

Argillaceous limestone,for Portland cement,114. 
Arizona, asbestos, 168 ; fluorspar, 173 ; garnet, 
195; molybdenum, 403; rubies (so 
called), 193 ; tungsten, 415 ; turquoise, 
194; vanadium, 416; weathering of 
ores, 281. 
Arkansas, bauxite in, 378; bituminous coal, 
analysis of, 7 ; coal fields, 29 ; fuller's 
earth, 175 ; lignite, 30 ; limonite, 271 ; 
manganese, 387 ; novaculite, 160 ; 
phosphate, 153 ; Portland cement ma- 
terials, 119 ; semi-bituminous coal, 
analysis of, 7 ; whetstone, 160 ; zinc 
ores, 315. 
Arkose, defined, 85. 
Arsenic, 398. 

distribution, Virginia, 398 ; Washington, 39S. 
in iron ores, 252. 
references on, 398. 
sources of, 398. 
uses, 398. 
with mercury, 393. 
Arsenopyrite, 398. 
Artesian water, 209. 

depth below surface, 209. 
distinction from ground water, 210. 
distribution, Atlantic coast, 210 ; Great 

Plains, 211 ; Mississippi Valley, 211. 
geologic horizon of, 209. 
in metamorphic rocks, 210. 
Asbestos, asbestos minerals, 167. 

amphibole, mode of occurrence, 167. 

as mineral pigment, 18S. 

chrysotile veins, origin, 168. 

distribution, 167 ; Canada, 168 ; Georgia, 167 ; 

North Carolina, 167 ; Virginia, 167. 
production, 169. 
references on, 169. 
serpentine, mode of occurrence, 167. 
uses, 169. 
Ashburner, on origin of petroleum, 44. 
Ash, coal, analyses of, 9. 
Ash in coal, 9. 
Ash soils, 214. 

Ash, volcanic, see Volcanic Ash. 
Asia Minor, turquoise in, 194. 
Aspen, Colo., lead-silver, 307, 367. 
Asphaltites, defined, 57. 
properties, 58. 
uses of, 61. 
Asphaltum, references on, 67. 
Astral oil, 56. 

Atlantic Ocean, analysis of water, 124. 
Azurite, 278, 281, 291, 293, 371. 



B 

Babbitt metal, 397. 

Bain, on Missouri lead-zinc ores, 317. 

Ball clay, defined, 99. 

distribution of, 103. 
Barite, as mineral pigment, 187. 

distribution, 170; Connecticut, 170; Mis- 
souri, 170; North Carolina, 170; 
Pennsylvania, 170 ; Tennessee, 170 ; 
Virginia, 170. 

mode of occurrence, 170. 

production, 170. 

references on, 171. 

uses, 170. 
Barre, Vermont granite, 77. 
Bauxite, analyses of, 376. 

distribution, Alabama, 376 ; Arkansas, 373 ; 
Georgia, 376 ; New Mexico, 379. 

production of, 380. 

properties, 375. 

references on, 383. 

uses, 380. 
Bavaria, lithographic stone, 182. 
Beaufort, S. C, phosphate deposits, 150. 
Beaumont, Texas, petroleum, 51. 
Becker, on mercury origin, 393. 
Bedding planes, effect on quarrying, 74. 
Belgium, buhrstones from, 161. 
Benzine, in petroleum, 42. 
Berea sandstone, 86. 
Bessemer ores, defined, 252. 
Bingham Canyon, Utah, copper, 296, 307. 
Bisbee, Ariz., copper, 290. 
Bismite, 399. 
Bismuth, distribution, Colorado, 399. 

ores, 399. 

production, 399. 

uses, 399. 
Bismuthinite, 399. 
Bismutite, 399. 
Bitumen, with mercury, 390, 393. 

with zinc, 315. 
Bituminous coal, price per ton, 34. 

properties of, 4. 

See Coal. 
Bituminous rocks, analyses, 61. 

California, described, 60. 

defined, 57. 

distribution, geographic, 57. 
geologic, 57. 

Indian Territory, mentioned, 60. 

Kentucky, mentioned, 60. 

origin, 57. 
Black copper, at base of gossan, 244. 
Black Hills, 8. Dak., tin, 411. 

tungsten, 415. 
Black Sea, analysis of water, 124. 
Black silver, 325. 
Blende, as contact ore, 235. 

See Sphalerite. 
Bluestone, defined, 85. 

See Building stones. 



INDEX 



421 



Bonanzas, 237, 286, 338, 345. 
Bone coal, 24. 
Boracite, 134. 
Borax, 134. 

marshes, California, 135. 

minerals containing, 134. 

near Daggett, 135. 

production, 136. 

references on, 135. 

uses, 135. 
Bornite, 278, 279, 2S6, 292. 

as contact ore, 235. 

secondary, 286. 
Bort, 192. 

Boulder, Colo., petroleum at, 53. 
Boulder, Mont., auriferous hot spring, 228. 
Bradford district, Pa., natural gas in, 54. 
Brass, 299, 320. 
Braunite, 383. 
Brazil, emerald, 193 ; magnetite sand, 258 ; 

monazite, 190; topaz, 194. 
Breaker, coal, 24. 
Brick clay, analysis of, 98. 

defined, 99. 

distribution of, 104. 
Brines, natural, 127. 
Britannia metal, 397. 
Brittle silver, 325. 
Bromyrite, 325. 
Bronze, 299. 

Brooks, on Lake Superior ores, 262. 
Brownstone, defined, 85. 
Buhrstones, characters, 161. 

distribution, 161. 

German, 161. 
Building stones, 69. 

absorption of, 73. 

color, 70. 

crushing strength, 72. 

cut off, 74. 

density, 70. 

distribution, see under Granite, Sandstone, 
Limestone, Marble, Slate. 

fading, cause of, 70. 

hardness, 71. 

lift, 74. 

permanent swelling, 73. 

porosity of, 73. 

production of, 89. 

properties of, 69. 

quarry water in, 73. 

references on, 90. 

resistance to frost, 73. 
to heat, 73. 

rift, 74. 

sap of, 73. 

specific gravity, 71. 

strength, 71. 

texture, 70. 
Bully Hill, Calif., copper, 298. 
Butte, Mont., copper ores, 282. 

metasomatism at, 284. 



C 

Calamine, 303, 305, 310, 313. 
Calaverite, 339. 

Calcareous clay, analysis of, 98. 
Calcite, see Gangue minerals. 
California, asbestos mentioned, 16S; coal, 31, 
32 ; copper, 297 ; fire clay, 103 ; infu- 
sorial earth, mentioned, 162 ; Kern 
Biver oil field, 53 ; lignite, analysis, 
7 ; lithium, 1S3 ; magnesite, 184 ; mag- 
netite, 256; manganese. 3S7 ; marble. 
82; mercury, 391 ; molybdenum, 408 ; 
natural gas, 56 ; petroleum, 52 ; petro- 
leum, characters, 53; platinum, 40S ; 
Portland cement materials, 119 ; salt, 
130 ; stoneware clay, 103 ; topaz, 194. 
Californite, as gem, 195. 
Calomel, 390, 391. 
Calumet conglomerate, 2SS. 
Cambrian, glass sand, 177. 
gold ores, 329. 
ocher, 1S7. 
silver ores, 329. 
tungsten, 415. 
Cambro-Silurian limonite, 271. 

pyrite, 199. 
Cannel coal, properties of, 5. 
Cape Nome, Alaska, 357. 
Carbonado, 192. 

Carboniferous, Appalachian section, 21; see 
Co;il. Anthracite, distribution ; cop- 
per, 290, 298, -296 ; gold ores. 886 ; 
gypsum, 140 ; hematite. 268 ; lime- 
stones for Portland cement, 119 ; 
petroleum, 68 ; salt, 129 ; shales for 
Portland cement, 119 ; siderite. JT:'. ; 
silver ores, 886 ; silver-lead, 365, 367, 
370; zinc ores, 314, 319. 
Carbonite. 25. 
Carborundum, 165. 
Cartersville, Ga., manganese, 3S6. 
Cassiterite, 410. 
Cat's eye (oriental), 194. 
Cavities, depth of occurrence, 229. 
fault, 23. 

formation of, 231. 
in earth's crust, 229. 
shrinkage, 231. 
solution. 231. 
Cement, calcareous, 109. 
hydraulic, defined, 111. 
natural, analyses, 113. 

difference from Portland, 113. 
properties of, 112. 
Portland, analyses of, 116. 
properties, 113. 
raw materials, 114. 
pozzuolano, defined, 111. 

composition, 111. 
production, 120. 
references, 121. 
Boman, 112. 



422 



INDEX 



Cement — continued. 
Rosendale, defined, 112. 
uses of, 119. 
Cement materials, natural rock, Appalachian 
region, 117 ; Illinois, 118 ; Kentucky, 
118 ; Maryland, 117 ; New York, 117 ; 
Ohio, 117; Pennsylvania, 117; Wis- 
consin, 118. 
Portland, Alabama, 119 ; Arkansas, 119 ; 
California, 119 ; Colorado, 119 ; Indi- 
ana, 119; Kansas, 119; Michigan, 
119; New Jersey, 118; New York, 
IIS ; North Dakota, 119 ; Ohio, 119 ; 
Pennsylvania, US; South Dakota, 
119 ; Texas, 119 ; Utah, 119. 
geologic age, 118. 
Cement plaster, 144. 
Cement rock, natural, analyses, 112. 
Cerargyrite, 325, 336. 
Cerium, in monazite, 191. 
Cerussite, 303, 305, 311, 371. 
Ceylon, graphite from, 179. 

topaz in, 194. 
Chalcocite, 278, 281, 285, 286, 291, 292, 297, 

298. 
Chalcocite, secondary, 2S6. 
Chalcopyrite, 278, 279, 281, 292, 293, 294. 
as a contact ore, 235. 
in pyrite deposits, 199. 
Chalk, 80. 

Champion Springs, N.Y., 205. 
Chara, as aid in marl formation, 119. 
Chester, Mass., emery deposits, 164. 
China clay, defined, 99. 
Chlorastrolite, as gem, 195. 
Chlorine, in soils, 214. 
Chlorite, 326. 

Chrome yellow, as mineral pigment, 188. 
Chromic iron, 399. 
Chromite, 399. 
analyses, 400. 
as mineral pigment, 188. 
associated rocks, 399. 
association with peridotite, 226. 
distribution in United States, 400 ; Cali- 
fornia, 401 ; North Carolina, 401 ; 
Pennsylvania, 401. 
origin of, 400. 
production of, 402. 
references on, 402. 
uses of, 401. 
with platinum, 408. 
Chrysocolla, 278, 281. 
Chrysoprase, as gem, 195. 
Chrysotile, 167. 
Chrysotile veins, origin, 168. 
Cinnabar, 390, 393. 
Cinnabar, as mineral pigment, 188. 
Classification of, clays, 98. 

ore deposits, 246. 
Clay, adobe, defined, 99. 
^Eolian, 95. 



air shrinkage, 96. 

alkalies in, 96. 

alumina in, 95. 

analyses of, 98. 

ball, distribution of, 103. 

classification of, 98. 

defined, 92. 

distribution, by kinds, 100. 

fire, distribution of, 104. 

fire shrinkage, 97. 

flood-plain, 94. 

fusibility of, 97. 

geologic distribution, 100. 

glacial, 94. 

glass pots, sources, 104. 

iron oxide in, 95. 

kaolin, defined, 99, 100. 

lake, 94, 104. 

lime in, 96. 

magnesia in, 96. 

marine, 94. 

miscellaneous, referred to, 104. 

origin, 92, 93. 

paper, sources, 104. 

physical properties, 96. 

plasticity of, 96. 

pottery," 99, 103. 

products, production of, 105. 

properties of, 95. 

references on, 106. 

residual, 104. 

sedimentary, 93. 

silica in, 95. 

specific gravity, 97. 

stoneware, distribution of, 103. 

sulphur trioxide in, 96. 

tensile strength, 96. 

titanic acid in, 96. 

uses of, 105. 

varieties, 99. 

water in, 96. 
Clay soils, properties, 215. 
Clausthal, Prussia, banded veins at, 237. 
Clifton, Ariz., copper, 293. 
Clinton limestone, gas in, 55. 
Clinton ore, 266. 

analyses, 268. 

Birmipgham, Ala., 266. 

character, 266. 

distribution, 266. 

origin, 267. 
Coal, 3. 

age of, 19. 

anthracite, defined, 5. 

bituminous, defined, 4. 

bone, 24. 

cannel, defined, 5. 

Carboniferous, distribution, 19. 

cretaceous, distribution, 19. 

distribution, Alabama, 20 ; Alaska, 32 ; 
Appalachian field, 20; Arkansas, 28, 
30 ; California, 32 ; Colorado, 31 ; 



INDEX 



423 



Coal, distribution — continued. 

Dakota, 31 ; Eastern Interior field, 26 ; 
Illinois, 27 ; Indiana, 27 ; Indian Ter- 
ritory, 29; Iowa, 29; Kansas, 29; 
Kentucky, 27; Maryland, 22; Michi- 
gan, 27 ; Montana, 31 ; New Mexico, 
31 ; Northern Interior field, 27 ; Ore- 
gon, 32 ; Pacific coast field, 31 ; Penn- 
sylvania, 22 ; Ehode Island field, 25 ; 
Eocky Mountain field, 30 ; South 
Dakota, 31 ; Southwestern field, 29 ; 
Texas, 30 ; Triassic area, 25 ; United 
States, 18 ; Washington, 32 ; Western 
Interior field, 29. 
elementary analysis, 14. 
faulting, 18. 

formation of, chemical changes during, 12. 
geologic distribution in United States, 19. 
heat and pressure, effect on, 14. 
kinds of, 3. 
origin of, 9. 
outcrops, 15. 
price per ton, 34. 
production of, 33. 

proximate analysis of, explained, 6. 
proximate analyses of United States coals, 6. 
references on, 35. 
rocks associated with, 16. 
seams, see Coal beds, 
semi-bituminous, defined, 5. 
Triassic, distribution, 19. 
Coal beds, pinching of, 16. 
splitting of, 17. 
structural features, 15. 
swelling of, 16. 
thickness of, 16. 
Coal-blossom, 16. 
Coal-brasses, 200. 
Coal-breaker, 24. 
Cobalt, Missouri, 404. 
ores, 404. 

production of, 406. 
references on. 407. 
uses, 406. 
Cobaltite, as mineral pigment, 188. 
Coke, natural, see Carbonite. 

production of, 35. 
Colemanite, 134. 

Colorado, anthracite coal, analysis of, S ; coal, 
31 ; coking coal, analysis of, 7 : cop- 
per. 298 ,• desilverized lead, 307 : fire 
clay, 103 ; lignite, analysis, 6 ; limon- 
iie, 271 ; magnetite, 256 ; manganese. 
888 ; petroleum, 53 ; Portland cement 
materials. 119; stoneware clay, 103; 
topaz,194; tungsten,415; uranium, 416. 
Comb structure, 237. 
Comstock lode, Nevada, 344. 
Conglomerate, copper-bearing, 2S8. 
Connecticut, barite, 170 ; garnet, 163 ; kaolin, 
101 ; lithium minerals, 1S3 ; tungsten 
in, 415. 



Contact deposits, copper ores, 293, 279. 

examples of, 235. 
Contemporaneous ores, in igneous rocks, 
224. 
in sedimentary rocks, 225. 
Copper, 278. 

in hot spring deposit, 228. 

in iron ores, 252. 

mode of occurrence in United States, 

279. 
native, 278, 279, 2S7, 2S9, 296. 
ores of, 278. 
production, 299. 
references on, 301. 
uses, 293. 

with mercury, 393. 
Copper ore, analysis, California, 298. 
analyses of, Montana. 285. 
distribution, 2S1 ; Alaska, 298; Appala- 
chian region, 294; Ariz., 290; Bis- 
bee, Ariz., 290; California, 297; 
Clifton, Ariz., 293; Colorado, 298; 
Connecticut, 296; Globe, Ariz.. 294; 
Idaho, 298 ; Jerome district, 292 ; 
Michigan. 2S7 ; Montana, 2S2 ; New 
Jersey, 296; New Mexico, 293; 
Pennsylvania, 296 ; Utah, 296 ; Wyo- 
ming, 293. 
Copper ores, gold and silver bearing, 328. 
impurities, 280. 
superficial alteration, 230. 
Coquina, 80. 

Corniferous limestone, gas in, 55. 
Cornwall, England, tin veins, 235. 
Cornwall, Pa., magnetite, 256. 
Corsicana, Texas, petroleum, 52. 
Corundum, ore of aluminum, 375. 
as abrasive, 163. 
distribution, 163. 
Georgia, 164. 
North Carolina, 164. 
mechanical concentration, 165. 
origin, 164. 
Cottonwood district, Utah, 307. 
Covellite, 285, 2S6. 

carrying platinum, 408. 
Creede, Colo., 307. 
Crested Butte, Colo., 15. 

Cretaceous, glass sand in, 176; greensand in, 
155 ; lignite, 19 ; limestone for lime, 
116; mercury, 392; petroleum, 53; 
phosphate, 153 ; shale for Portland 
cement, 119. 
Crimora. Ta., manganese, 3S5. 
Cripple Creek, Colo., gold, 33S. 
Crustification, defined, 236. 
Cryolite. 375. 

Crystal Falls district, hematite, 261. 
Culm, defined, 24. 

uses, 24. 
Cuprite, 273, 291. 
Cut-off, in quarries, 74. 



424 



INDEX 



Dakota, lignite in, 31. 
Dead Sea, analysis of water, 124. 
Descension theory, 240. 
Devonian, phosphate in, 153. 
Diamond, properties of, 192. 

South Africa, 192. 

United States, 192. 
Didymium in inonazite, 191. 
Dismal Swamp, analysis of peat from, 6. 
Disseminated ores, 242. 
Dolomite, see Gangue. 

defined, 78. 

petroleum in, 51. 
Douglas Island, Alaska,, 354. 
Dredging gold, 348. 
Drift mining, gold, 347. 
Duck River, Tenn., phosphate deposits, 151. 
Ducktown, Tenn., copper at, 295. 
Dune soils, 214. 



Eagle Pass, Texas, coal, 30. 
Earthenware clay, defined, 99. 
Earth's crust, zones in, 22S. 
Eldridge, on Florida phosphate, 149. 
Embolite, 325. 

Emerald, distribution, Brazil, 194 ; Ceylon, 193 : 
Hindostan, 193; North Carolina, 193; 
Siberia, 193. 

lithia, 194. 

properties, 193. 
Emery, defined, 163. 

Massachusetts, described, 164. 

New York, mentioned, 164. 
Emmons, cited, 230. 
Enargite, 278, 279, 2S4, 372. 
England, fuller's earth in, 175. 
Epidote, 295, 326. 

in contact deposits, 235. 



Faults, effect on oil reservoir, 53. 

relation to oil springs, 53. 
Feather River, Calif., gold in, 349. 
Ferric sulphate, as a solvent of ores, 244. 

effect on pyrite, 244. 
Ferro-chromium, 401. 
Ferro-nickel, 401. 
Ferro-titanium, 414. 
Fertilizers, apatite, 147. 

fisted, 147. 

production of, 156. 

references on, 157. 

See Phosphate, Guano, Gypsum, and 
Greensand. 
Findlay, Ohio, oil pressure at, 45. 
Fire clay, analysis of, 98. 

denned, 99. 

distribution in United States, 102. 

under coal, 16. 



Fissure veins, apex, 239. 

bonanzas, 237. 

boundaries of, 236. 

comb structure, 237. 

filling of, 240. 

foot wall, 239. 

hanging wall, 239. 

linked, 239. 

lode, 239. 

ores common in, 237. 

secondary banding, 236. 

selvage in, 237. 

strike of, 239. 
Fixed carbon, effect of, in coal, 8. 
Flagstone, defined, 85. 
Flats, 312. 

Flint clay, defined, 99. 
Florence oil field, Colorado, 53. 
Florida, ball clay, 103 ; phosphate, 148 ; phos- 
phate, uses, 154. 
Fluorspar, characters, 171. 

distribution, Arizona, 173 ; Illinois, deposits 
described, 172 ; Kentucky, 173 ; Ten- 
nessee, 173. 

gangue mineral, 172. 

gems, 195. 

occurrence, 171. 

origin, 173. 

production, 173. 

references on, 173. 

uses, 173. 
Foot wall, 239. 

Fort Dodge, Iowa, gypsum at, 140. 
Foster, on Lake Superior ores, 262. 
Fountain head, 209. 
France, buhrstones, 161. 
Franklinite, 303, 304, 308, 310. 
Fredonia, N.Y., gas, 40. 
Freestone, defined, 85. 
Freiberg, Saxony, banded veins at, 237. 
Fuel ratio, 8. 
Fuller's earth, analyses of, 175. 

difference from clay, 174. 

distribution, Alabama, 175 ; Arkansas, 175 ; 
England, 175; Florida, 175; Ne- 
braska, 175; New York, 175; South 
Dakota, 175. 

geological distribution, 175. 

production of, 176. 

properties, 174. 

references on, 176. 



Gaffney, S.C., tin, 411. 
Galena, as a contact ore, 235. 

mentioned, 303, 305, 306, 311, 312, 313, 315, 
329, 365, 370, 371, 372, 373, 412. 
Galicia, ozokerite in, 59. 
Galvanic action, ore precipitation by, 235. 
Gangue minerals, barite, 311, 315, 336,342, 365, 
367, 372. 
calcite, 311, 312, 315, 342, 365, 390, 393, 396. 



INDEX 



425 



Gangue minerals — continued. 

chert, 315, 365. 

dolomite, 311, 315, 339, 342, 367. 

epidote, 295, 412. 

fluorite, 311, 339, 410, 412. 

garoet, 295. 

lepidolite, 410. 

marcasite, 312, 313. 

muscovite, 410. 

orthoclase, 339, 344. 

quartz, 311, 335, 336, 339, 342, 344, 367. 370, 
372, 373, 390, 396, 412. 

rhodochrosite, 342, 370, 383. 

topaz, 410, 412. 

zinnwaldite, 412. 
Garnet, as an abrasive, 163. 

as a gem, 194. 

distribution, Arizona, 195; Connecticut, 
mentioned, 163; India, 194; New 
Mexico, 195 ; New York, mentioned, 
163; North. Carolina, 195; Tennessee, 
163. 

in contact deposits, 235. 

uses as abrasive, 163. 
Gash veins, in Wisconsin, 240. 

defined, 240. 
Gasoline, in petroleum, 42. 
Genthite, 404. 

Georgia, asbestos, 167 ; bauxite, 376 ; corun- 
dum, 164; graphite, 179; manganese, 
385 ; ocher, 187 ; phosphate, 154 ; 
stoneware clay, 103. 
German silver, 321. 
Germany, buhrstones from, 161. 
Gibbsite, 375. 
Gilsonite, 59. 

analysis of, 60. 

occurrence, 59. 

properties, 59. 
Glacial soils, 214. 
Glass sand, analyses of, 177. 

distribution, Illinois, 177 ; Iowa, 177; Mary- 
land, 177 : Massachusetts, 177 ; New 
Jersey, 177 ; Pennsylvania, 177 ; West 
Virginia, 177. 

effect of clay in, 176. 

effect of iron oxide on, 176. 

geologic distribution, 176. 

production, 177. 

properties, 176. 

references on, 178. 
Glauber salt, 136. 
Globe, Ariz., copper, 294. 
Gold, gravels, 346. 

gravels, Pacific Coast, 347. 
Gold Hill, N.C., copper at, 295. 
Gold, in beach sands, 349. 

native, 325, 336, 339, 365. 
Gold ores, chlorination process, 330. 

classification, 327. 

cyanide process, 330. 

distribution, Alaska, 353 ; Alaska, placer 



deposits, 356 ; Black Hills. 350 : Crip- 
ple Creek, Colo., 338; Cordilleran re- 
gion, 332 ; Homestake belt, S. Dak., 
351 ; Idaho, 337 ; Mercur, Utah, 336 ; 
Michigan, 352 ; Montana, 337 ; Mother 
Lode belt, Calif., 333; Nevada Co., 
Calif.. 334 ; Oregon, 335 ; Pacific coast 
belt, 332 ; "Washington, 335. 

eastern crystalline belt, 352. 

extraction, 329. 

free milling, defined, 329. 

geologic distribution, 329. 

gold-milling centres, 330. 

igneous rocks associated with, 326. 

in igneous rocks, 326. 

in metamorphic rocks, 326. 

in propylitic veins, 326. 

listed, 325. 

mode of occurrence, 326. 

production of, 35S. 

quartzose, 32S. 

quartz veins, 326. 

references on, 360. 

refractory, defined, 329. 

sands in arid regions, 349. 

secondary enrichment of. 82T. 

siliceous, Cambrian, South Dakota, 352. 

uses of, 357. 

valuation of, 330. 

wall rocks, 326. 

weathering of, -V2~. 

with mercury, 393. 

with platinum, 408. 
Gold-silver ores, distribution, Bohemia district, 
Ore., 345; Boulder Co., Colo., 345; 
Central Belt, 335; Clear Creek Co., 
Colo., 345; Comstock lode, Nev., 
344 ; Eastern Belt, Tertiary ores, 337 ; 
Gilpin Co., Colo., 345; Monte Cristo, 
Wash., 345; Ouray, Colo., 342 : Owy- 
hee Co., Ido.,345: San Juan region, 
Colo., 341 ; Silverton, Colo., 341 ; Tel- 
luride, Colo., 342 ; Tonopah, 343. 
Gold veins, associations with igneous rock, 230. 
Gossan, defined, 242. 

leaching of, 244. 
Grahamite, analysis of, 60. 

occurrence, 59. 
Grand Rapid s, Mich., gypsum at, 142. 
Granites, 75. 

characteristics of, 75. 

color of, 75. 

distribution, California, 77; Central States, 
77 : eastern crystalline belt, 77 : Min- 
nesota. 77 ; Missouri, 77 : Montana, 
77 ; Oregon, 77 ; South Dakota. 77 ; 
Texas, 77 ; United States. 77 ; Wash- 
ington, 77 ; western states, 77. 

durability of, 75. 

geologic range, 76. 

uses of, 77. 

weight of, 75. 



426 



INDEX 



Graphite, amorphous, 179. 

amorphous, Khode Island, 179. 

analysis, 17S. 

artificial, 180. 

as mineral pigment, 188. 

distribution, Alabama, 179 ; Ceylon, 179 ; 
Ceylon, origin, 179 ; Georgia, 179 ; 
Michigan, not such, 179 ; Montana, 
179 ; New Hampshire, 179 ; New 
York, 179; North Carolina, 179; 
Pennsylvania, 179 ; Wisconsin, not 
such, 179. 

occurrence, 178. 

production, 180. 

properties of, 178. 

references on, 181. 

uses, 179. 
Grass Valley, Calif., 334. 

banded veins at, 237. 
Gravels, auriferous, 346. 
Gravity of petroleum, 41. 
Great gossan lead, 295. 
Great Salt Lake, analysis of water, 124. 
Greenland, cryolite in, 375. 
Greensand, analyses, 156. 

defined, 155. 

distribution, 155. 

source of Texas liraonite, 271. 

Virginia, uses of, 155. 
Greisen, tin bearing, 410. 
Grindstones, distribution, 159. 

properties of, 158. 
Ground water, 208. 

movements of, 208. 
Guano, 155. 

bat, 155. 

bat, analysis, 155. 

bat, Texas, 155. 

kinds, 155. 

Peru, 155. 

West Indies, 155. 
Gumbo clay, defined, 99. 
Gypsite, defined, 139. 

distribution, Kansas, 141 ; Oklahoma, 142 ; 
Texas, 142 ; Wyoming, 142. 

origin of, 140. 
Gypsum, absence from Kansas salt beds, 130. 

analyses before and after calcination, 144. 

analyses of, 143. 

as mineral pigment, 187. 

calcination process, 144. 

composition, 139. 

distribution, Arizona, 142 ; California, 142 ; 
Colorado, 142 ; Idaho, 142 ; Iowa, 140 ; 
Kansas, 141 ; Michigan, 142 ; Mon- 
tana, 142 ; Nevada, 142 ; New York, 
142 ; Ohio, 142 ; South Dakota, 142 ; 
Vermont, 142 ; Virginia, 142. 

formed from pyrite, 140. 

formed from sea-water, 140. 

geologic distribution, 139. 

occurrence, 139. 



origin, 139. 
production of, 145. 
references on, 146. 
uses, 143. 
volcanic origin of, 140. 



Hamilton shales, for Portland cement, 118. 

Hanging wall, 239. 

Hayes, on Arkansas bauxite, 379. 

on Georgia bauxite, 376. 

on Tennessee phosphates, 153. 
Hematite, 259. 

analysis, Lake Superior, 264. 

as mineral pigment, 186. 

distribution, Alabama, 268 ; Lake Superior 
region, 259; Missouri, 269; Utah, 
268; Wyoming, 268; United States, 
259. 

in contact deposits, 235. 

with mercury, 398. 

See Clinton ore. 
Hermann, on weight of stones, 71. 
Hindostan, emerald in, 193. 
Hindostan stone, 160. 
Holston Valley, Va., gypsum, 142. 
Horn silver, 325. 
Hot spring, gold-bearing, 228. 
Hot spring deposits, see Stibnite, Pyrite, 

Copper. 
Hot Springs, 204. 
Hiibnerite, 414. 
Humus, 213. 
Hungary, opal in, 195. 
Huronian, iron ores in, 261. 
Hydraulic limes, see Lime. 
Hydraulic mining, 348. 

I 

Idaho, auriferous lead ores in, 329 ; copper, 
298 ; nickel, 405 ; silver-lead ores, 372. 

Idaho basin, Idaho, 337. 

Igneous rocks, miscellaneous, for building, 78. 

Illinois, brick clays, 104 ; bituminous coal, 
analysis of, 7 ; poal field, 26 ; glass 
sand, 177 ; natural rock cement, 118 ; 
ocher, 187 ; sienna, 187 ; stoneware 
clay, 103. 

Ilmenite, 257, 413. 

India, garnet in, 194. 
source of mica, 186. 

Indiana, Brazil coal, analysis of, 7 ; brick clays, 
104 ; cannel coal, analysis of, 7 ; coal 
field, 27 ; petroleum, distillates from, 
42 ; natural gas, 55 ; natural gas analy- 
sis, 43 ; petroleum, 50 ; Portland ce- 
ment materials, 119 ; stoneware clay, 
103 ; whetstones mentioned, 160. 

Indian Territory, coal field, 29 ; natural gas, 
55. 

Infusorial earth, defined, 162. 

distribution, California, 162 ; Maryland, 162 ; 



INDEX 



427 



Infusorial earth, distribution — continued. 

Missouri, 162 ; • Nevada, 162 ; New- 
England, 162 ; New York, 162 ; Vir- 
ginia, 162. 

German deposits, 162. 

uses, 162. 
Iowa, bituminous coal, 7 ; coal in, 29 ; glass 
sand in, 177 ; gypsum, 140 ; lime rock 
in, 116 ; limonite in, 271 ; lithographic 
stone in, 1S2 ; stoneware clay in, 103 ; 
zinc ores in, 311. 
Iridium, properties and occurrence, 410. 

uses, 410. 

with platinum, 407. 
Iron, in copper ores, 280. 
Iron Mountain, Calif., copper, 298. 
Iron ores, distribution, Alabama, 266, 271 ; 
Arkansas, 271; California, 256; Colo- 
rado, 256, 257 ; Iowa, 271 ; Kentucky, 
273; Michigan, 256, 261, 265; Minne- 
sota, 257, 261, 264, 271 ; Missouri, 
269; New Jersey, 256, 257; New 
Mexico, 256, 268; New York, 255, 
257, 258, 266, 273; North Carolina, 
255 ; Ohio, 266, 273 ; Oregon, 271 ; 
Pennsylvania, 256, 273 ; Sweden, 270 ; 
Texas," 271 ; Utah, 256, 268 ; Ver- 
mont, 271 ; Virginia, 271 ; Wisconsin. 
261, 266, 271 ; Wyoming, 256, 268. 

distribution in United States, 254. 

geologic distribution, 254. 

impurities in, 252. 

magnetite, modes of occurrence, 254. 

magnetites, origin of, 255. 

modes of origin, 253. 

non-titaniferous, 254. 

production of, 273. 

references on, 276. 

See Hematite and Limonite. 
Iron oxide, effect on clay, 95. 

in soils, 214. 
Irving, on Lake Superior ores, 262. 



Japan, solfataric sulphur in, 196. 
Jenney, on Missouri lead zinc ores, 317. 
Jennings, La., petroleum, 52. 
Jerome, Ariz., copper, 292. 
Jet, 4. 

Joplin, Mo., zinc ores, 308, 314. 
Josephinite, 408. 

Jurassic, gold, 333 ; lithographic stone, 182 ; 
sulphur in, 197. 

K 
Kansas, coal, 29 ; gypsite, 141 ; gypsum, 141 ; 
lime rock, 116 ; natural gas, 55 ; petro- 
leum, 52; petroleum, distillates from, 
42 ; Portland cement materials, 119 : 
salt, 130. 
Kaolin, defined, 99. 
analysis of, 98, 101. 



distribution, Alabama, 101 ; Connecticut, 
101 ; Maryland, 101 ; North Carolina, 
101; Pennsylvania, 101; Virginia, 
101. 
origin, 93. 

Kaolinite, 92. 
analysis of, 98. 
product of metasomatism, 326. 

Kemp, cited, 230, 246, 257, 310, 407. 

Kentucky, ball clay in, 103; bat guano, 155; 
bituminous coal, analysis of, 7 ; coal 
field, 27 ; fluorspar, 173 ; lithographic 
stone, 182; molding sand, 190; natu- 
ral gas, 56 ; natural rock cement, 118 ; 
stoneware clay, 103. 

Kerosene, in Wyoming petroleum, 53. 

Kerosene shale, 57. 

Keweenaw series, Michigan, 287. 

Klondike River, Alaska, 354, 356. 

Knox dolomite, 376. 

Kunzite, as gem, 195. 



Lake asphalt, 59. 

Lake Superior ores, 259. 

analyses, 264. 

character, 260. 

development, 265. 

origin, 263. 
Lanthanum, in monazite, 191. 
Lateral secretion theory, 240. 
Lead, desilverized, occurrences, 307. 

gangue minerals of, 304. 

ores of, 303. 

production of, 321. 

references on, 323. 

uses of, 319. 

with mercury, 393. 
Lead ores, Colorado, 307. 

disseminated, 306. 

distribution, Appalachian belt, 306; Mis- 
souri, 306, 314 ; Eocky Mountain 
states, 318. 

gold and silver bearing, 328. 

impurities in, 304. 

modes of occurrence, 304. 

superficial alteration, 305. 
Leadville, Colo., 364. 
Lepidolite, 183. 

Lesley, on origin of petroleum, 44. 
Lift, in quarries, 74. 
Lignite, 4. 

age of, 4. 

areas in United States, 19. 

Gulf States area, 30. 

properties of, 4. 
Lime, effect on clay, 96. 

effect on soils, 215. 

in iron ores, 252. 

properties, 110. 

references on, 121. 

uses of, 119. 



428 



INDEX 



Limes, hydraulic, distribution, 117. 

properties of, 112. 
Limestone, analyses, 109. 

burning, changes in, 110. 

Cretaceous, for building, 80. 

distribution in United States, 80. 

for lime, distribution, 116. 

for Portland cement, 114, 118. 

general characteristics, 78. 

lithographic, 181. 

varieties, 78. 

See Building stones. 
Limonite, 269. 

advantage of using, 272. 

analyses of, 272. 

bog ores, 269. 

Cambro-Silurian, 271. 

distribution, Appalachian, 271 ; Arkansas, 
271 ; Colorado, 271 ; Iowa, 271 ; Min- 
nesota, 271 ; Oregon, 271 , Texas, 
271 ; Wisconsin, 271. 

Great Gossan Lead, 271. 

manganiferous, 271. 

residual,. 270. 

with mercury, 393. 
Lindgren, cited, 230. 

on Colorado gold ores, 837. 
Linked veins, 239. 
Linnaeite, 404. 
Lipari, pumice from, 162. 
Litharge, 319. 

Lithium, distribution, California, 1S3 ; Connec- 
ticut, 183 ; South Dakota, 183. 

industry, 183. 

minerals as sources of, 183. 

production, 183. 

uses, 183. 
Lithographic stone, analyses, 181. 

definition, 181. 

distribution, Bavaria, 182 ; Iowa, 182 ; Ken- 
tucky, 182. 

physical properties, 1821 

references on, 183. 
Lithophone paint, 170. 
Lode, 239. 
Loess, defined, 99. 
Louisiana, petroleum, 52 ; salt, 129 ; sulphur, 

197. 
Lower Carboniferous, fluorspar in, 172. 
Lower Helderberg, limestone for lime, 116. 



M 

Magmatic segregation, 224. 

in acid rocks, 225. 

in basic rocks, 224. 

of copper, 279. 
Magmatic water, effects of, 230. 
Magnesia, effect on clay, 96. 

in iron ores, 252. 

in natural cements, 113. 

in soils, 214. 



Magnesite, California, 184. 

occurrence and properties, 183. 

production, 184. 

references on, 184. 

uses, 184. 
Magnetite, as a contact ore, 235. 

non-titaniferous, 254. 

sand, 258 ; see Iron ores. 

titaniferous, 257. 
analyses, 258. 
distribution, 257. 
origin, 257. 
Maine, molybdenum, 403 ; topaz, 194. 
Malachite, 278, 281, 291, 293, 371. 
Malay peninsula, tin from, 412. 
Maltha, analysis of, 60. 

Manganese, distribution, Arkansas, 387 ; Cali- 
fornia, 387; Colorado, 388; eastern 
area, 385; Georgia, 385; Utah, 388; 
Virginia, 386. 

in iron ores, 252. 

ores of, 383. 

origin, 384. 

production, 388. 

references on, 389. 

uses, 388. 
Marbles, distribution in United States, 81. 

general characteristics, 78. 

See Building stones. 
Marl, for Portland cement, 114, 119. 
Marquette range, 261, 263. 
Marsh gas, in natural gas, 42. 

properties, 42. 
Marshes, salt, cause of, 127. 
Maryland, coal, referred to, 37 ; glass sand, 177 ; 
infusorial earth, 162; kaolin, 101; 
marble, 82 ; natural rock cement, 118. 
Marysville, Mont., 337. 
Massachusetts, emery in, described, 164 ; glass 

sand, 177 ; marble, 82 ; pyrite, 199. 
Mechanical concentration, 289, 310, 313, 

315. 
Mediterranean Sea, analysis of water, 124. 
Melaconite, 27S, 295. 
Mendeljeff, on petroleum origin, 46. 
Menominie range, 261. 
Mercur, Utah, 336. 
Mercury, 390. 

associated minerals, 393. 

distribution, California, 390; Oregon, 392; 
Texas, 392. 

extraction, 394. 

mode of occurrence, 890. 

ores of, 390. 

origin, 393. 

production of, 394. , 

references on, 395. 

uses, 393. 
Merrill, G. P., on chrysotile veins, 169. 
Mesabi range, Minnesota, 261, 262. 
Mesozoic, auriferous gravels, 327 ; clays of, 100 ; 
petroleum, 53 ; quartzose ores, 328. 



INDEX 



429 



Metals, disseminated in granite, 226. 

disseminated in limestone, 226. 

disseminated in quartz-porphyry, 226. 

distribution in rocks, 226. 

precipitation, conditions governing, 232. 
Metasomatism, defined, 233. 

pressure accompanying, 233. 

temperature during, 233. 

variation in process of, 233. 
Meteoric waters, importance in secondary con- 
centration, 230. 
Mexico, opal in, 195 ; solfataric sulphur in, 196. 
Mica, distribution, North Carolina, 185. 

in kaolin, 100. 

mode of occurrence, 185. 

production of, 185. 

references on, 186. 

species of economic value, 185. 

value of, 185. 
Micanite, 185. 

Michigan, bituminous coal, analysis of, 7 ; 
brick clays, 104 ; coal field, 28 ; cop- 
per ores, 287 ; gold, 352 ; graphite, so- 
called, 180; gypsum, 142; magnetite, 
256 ; Portland cement materials, 119 ; 
salt in, 129. 
Millerite, 404. 
Millstones, characters, 161. 

distribution, 161. 
Mine Hill, N.J., zinc ore, 309. 
Mine waters, analyses of, 227. 

vadose, 227. 
Mineral pigments, 186. 

asbestos, 188. 

barite, 187. 

graphite, 188. 

gypsum, 187. 

hematite, 186. 

ochers, 186. 

production, 1S8. 

references on, 189. 

slate, 1S7. 
Mineral springs, volume of discharge, 205. 
Mineral waters, analyses, 206. 

classification, 205. 

defined, 204. 

distribution, 205. 

origin and occurrence, 204. 

production of, 206. 

references on, 207. 

thermal springs, 204. 
Mineralizing vapors, 234. 

in contact deposits, 235. 
Minerals, in contact deposits, 235. 
Minnesota, hematite, 261, 264 ; limonite, 271. 
Miocene, petroleum, 53 ; phosphate, 150. 
Mississippi, lignite in, 30. 
Mississippi delta, soils of, 214. 
Missouri, bituminous coal, analysis of, 7 ; ball 
clay, 103 ; barite, 170 ; hematite, 269 : 
infusorial earth, 162 ; lime rock, 116 ; 
stoneware clay, 103. 



Moisture in coal, 8. 
Molding sand, analysis, 189. 

distribution, 190. 

mechanical composition, 189. 

properties, 189. 

references on, 190. 
Molybdenite, 339, 403. 
Molybdenum, 403. 

in Maine, 403. 

in western states, 403. 

ores and occurrences, 403. 

production of, 403. 

references on, 403. 

uses, 403. 
Monazite, analyses, 191. 

composition, 190. 

distribution, Brazil, 190; North Carolina, 
190 ; South Carolina, 190. 

magnetic separation of, 191. 

occurrence, 190. 

production of, 191. 

references on, 191. * 

uses, 191. 
Montana, asbestos, 16S ; silver, 2S4 ; coal, 31 ; 
copper ores, 2S2 ; graphite, 179 ; liirnite 
analysis from, 6 ; molybdenum, 403 ; 
sapphire. 198 ; silver-lead ores, 373. 
Monte Cristo, Wash., 335. 

direction of veins at, 238. 
Montezuma, Colo., zinc concentrates, 319. 
Moss agate, as gem, 195. 
Mother lode, California, gold, 333. 
Muscovite, as source of mica, 1S5. 

N 

Naphthas, in petroleum, 42. 

Natural gas, analyses of, 43. 

anticlinal theory, 43. 

distribution, California, 56; Indiana, 55; 
Indian Territory, 55; Kansas, 55; 
Kentucky, 56 ; New York, 54 ; Ohio, 
55 ; Pennsylvania, 54 ; Texas, 56 ; 
"West Virginia, 55. 
exhaustion of, 54. 
geologic distribution, 48. 
history of development, 40. 
occurrence of, 43. 
pressure in well, 44. 
properties of, 42. 
references on, 67. 
uses of, 56. 
Natural rock cements, see Cements. 
Nebraska, fullers earth in, 175. 
Nevada, infusorial earth, mentioned, 162 ; mag- 
matically segregated ores in, 225 ; sol- 
fataric sulphur, 197 ; silver-lead ores, 
373 ; tungsten in, 415. 
Nevada City, Calif., 334. 

Newberry, on temperature petroleum forma- 
tion, 47. 
New Brunswick, albertite in, 59. 
New Caledonia, nickel supply from, 405. 



430 



INDEX 



New England, infusorial earth, mentioned, 162. 
lime rock in, 116. 

New Hampshire, graphite in ; 179 ; whetstones 
mentioned, 160. 

New Jersey,ballclay,103; copper,296; glass sand, 
177; greensand, 155; magnetite, 256 ; 
molding sand, 190 ; Portland cement 
materials, 118 ; stoneware clay, 103. 

New Mexico, anthracite coal, analysis of, 8 ; 
bauxite, 379 ; coal, 30, 31 ; copper, 
298; garnet, 195; magnetite, 256; 
molybdenum, 403 ; silver-lead ores, 
373 ; turquoise, 194 ; vanadium, 416. 

New York, Clinton ore, 266 ; emery, mentioned, 
164 ; fuller's earth, 175 ; garnet, 163 ; 
graphite, 179 ; gypsum, 142 ; infuso- 
rial earth, mentioned, 162 ; limestone ; 
116 ; magnetite, 255 ; marble, 82 ; mill- 
stones, 161 ; molding sand, 190 ; natu- 
ral gas, 54 ; natural rock cement, US ; 
petroleum occurrence, 48; Portland 
cement materials, 118 ; production of 
gypsum, 145; pyrite, 199; salt, 127; 
siderite, origin of, 273 ; sienna, 187 ; 
talc, 202 ; whetstones, mentioned, 160. 

New Zealand, magnetite sand, 258. 

Niccolite, 404. 

Nickel ores, 404. 

Nickel, analysis of, 405. 

distribution, Missouri, 404 ; North Carolina, 
404; Ontario, Canada, 404; Pennsyl- 
vania, 404 ; western states, 404. 
production of, 406. 
references on, 407. 
uses of, 405. 

Nile Valley, alluvial soils. 214. 

Nitrogen, in natural gas, 214. 
in soils, 214. 

Norite, New York, 78. 

North Carolina, asbestos, 167 ; barite, 170 ; 
corundum, 164 ; emerald, 193 ; garnet, 
195 ; graphite, 179 ; kaolin, 101 ; mag- 
netite, 255; mica in, 185; millstones 
in, 161 ; monazite in, 190 ; phosphate 
in, 154 ; pyrophyllite, 203 ; rubies, 193 ; 
talc, 201 ; tin, 411 ; Triassic coal, 25. 

North Dakota, Portland cement materials, 119. 

Norway, titanium in, 413. 

Novaculite, 160. 
origin, 160. 

Nuggets, gold, 346. 

O 

Ocher, as mineral pigment, 186. 
classification, 187. 
composition, 187. 
distribution, 187. 
origin, 187. 

Ochsenius, on origin of salt, 125. 

Ogdensburg, New Jersey, zinc ore, 309. 

Ohio, brick clays, 104 ; brines, 129 ; Clinton 
ore, 266 ; gypsum, 142 ; Hocking 
Valley coal, analysis of, 7; molding 



sand, 190 ; natural gas analysis, 43 ; 
natural gas, 55 ; natural rock cement, 
118 ; petroleum, 50 ; Portland cement 
materials, 119 ; siderite, 273 ; stoneware 
clay, 103 ; whetstones, mentioned, 160. 
Oil rock, capacity of, 44. 
Oil shales, analysis, 57. 
distillation of, 57. 
geographic distribution, 57. 
properties, 56. 
references on, 67. 
Oil springs, 52. 
Oilstones, defined, 159. 

distribution, 160. 
Oklahoma, gypsite in, 142. 
Oliphant, on petroleum distillates, 42. 
Ontario, anthraxolite in, 59. 
Ontario, nickel, 404. 
Onyx marbles, 83. 
characters, 83. 
distribution, 83. 
for lithographic work, 182. 
references on, 91. 
Oolitic, limestone, defined, 80. 
Opal, composition and occurrence, 195. 

distribution, Hungary, 195 ; Mexico, 195 ; 
Oregon, 195 ; Washington, 195. 
Orange Spring, Fla., 205. 
Ordovician, lead in, 306 ; limestones, 116. 
Ore deposits, bedded, 241 ; bonanzas, forma- 
tion of, 245 ; chamber deposits, 242 ; 
classification of, 246 ; contact de- 
posits, 241 ; contemporaneous origin 
of, 224 ; disseminations, 242 ; Fahl- 
band, 241 ; fissure veins, 236 ; forms 
of, 236 ; impregnations, 241 ; linked 
veins, 239 ; ore channel, 241 ; origin 
of, 224 ; oxidation, 243 ; oxidation, 
depth of, 244, references on, 249 ; sec- 
ondary alteration in, 242 ; secondary 
enrichment, 245 ; weathering, 242 ; 
weathering, chemical changes, 243 ; 
weathering, conditions affecting depth, 
243 ; weathering, minerals affected, 242. 
Oregon, coal, 32 ; gold ores, 335 ; limonite, 27 ; 
mercury, 392 ; nickel, 404 ; opal in, 
195 ; solfataric sulphur, 197. 
Ores, concentration in rocks, 225. 

value of, 245. 
Organic matter, as reducing agent, 317. 
Oriskany, glass sand in, 177 ; limonite in, 271 ; 

phosphate in, 153. 
Orpiment, 398. 

Orton, on petroleum origin, 47. 
Osmium, properties and occurrence, 409. 
uses, 409. 

with platinum, 407. 
Osmotic pressure, ore precipitation by, 236. 
Ouray, Colo., 307, 342. 
Ozark region, 314. 
Ozokerite, properties, 59. 
occurrence, 59. 



INDEX 



431 



Palladium, properties and occurrence, 409. 
uses, 409. 

with platinum, 407. 
Paper clay, defined, 99. 
Paraffin, 56. 
Paragenesis, 313, 315. 
Park City, Utah, 30T. 
Peace River, Fla., phosphate, 148. 
Peale, on mineral waters, 205. 
Peat, analyses of, 4, 6. 
defined, 3. 
references on, 38. 
sections in bog, 3. 
Peckhara, on temperature petroleum forma- 
tion, 47. 
Pegmatite, tin-bearing, 410. 
Pennsylvania, anthracite coal, 8, 22; barite, 
170; bituminous coal, 7; cement ma- 
terials, 117, 118 ; chromite, 401 : Clin- 
ton ore, 266; copper, 296; fire clays, 
102 ; glass sand, 177 ; graphite, 179 ; 
iron ore, 256, 273 ; kaolin, 101 : mag- 
netite, 256 ; natural gas, 54 ; ocher, 
187 ; petroleum, 50 ; phosphate, 154 ; 
Portland cement materials, 118 ; ser- 
pentine, 84 ; siderite, 273 ; sienna, 
187 ; stoneware clay, 103 ; titanium, 
414; zinc, 311. 
Penokee-Gogebic range. 261, 262. 
Penrose, on Georgia manganese, 3S6. 
Pentlandite, 404. 
Permian, gypsum, 141; rock salt, 127; salt, 

130. 
Persia, turquoise, 194. 
Petroleum, analyses, 41. 
anticlinal, 43. 
asphaltic, 40, 42. 

uses, 42. 
boiling point, 42. 
distillates, percentages of, 42. 
distribution, Alaska, 54 ; Appalachian field, 
48 ; California, 52 ; Colorado, 53 ; 
Kansas, 52 ; Ohio-Indiana, 50 ; Penn- 
sylvania, 50 ; Texas-Louisiana, 51. 
flashing point. 41. 
geologic distribution, 48. 
gravity of, 41. 

gushers, in Beaumont field, 45. 
history of development, 39. 
movement in rocks, 47. 
nitrogen in, 40. 
origin, inorganic theory, 46. 

organic theory, 46. 
paraffin in, 42. 
pool, defined, 44. 
pressure in well, 44. 
production, 62. 
properties of, 40. 
references on, 66. 
rock pressure, 45. 
sands, defined, 44. 



solidification temperature, 41. 

uses of, 56. 

wells, depth of, 45. 
Phlogopite, as source of mica, 185. 
Phosphate, analyses, 154. 

distribution, Alabama, 153 ; Arkansas, 153 ; 
Florida, 14S ; Georgia, 153; North 
Carolina, 153; Pennsylvania, 153; 
South Carolina, 150 ; Tennessee, 150. 

geological distribution, 148. 

impurities, 153. 

land pebble, 149. 

mode of occurrence, 147. 

river pebble, 149. 

rock, 14S. 

soft, 149. 

uses, 154. 
Phosphoric acid, in soils, 214. 
Phosphorus, in copper ores, 280. 

in iron ores. 252. 
Pipe clay, defined. !>f». 
Pipe lines, West Virginia, 55. 
Pitches, 312. 
Placers, 327. 
Plaster of Paris, 144. 
Plasticity, clay, 96. 
Platinum, associated metals, 407. 

composition, 4oT. 

distribution, California, 408; "Wyoming, 
108. 

native, 407. 

ores, 407. 

production, 408. 

references on, 408. 

uses, 408. 
Pleistocene, clays, 100; glass sand, 176 ; stone- 
ware clays. 103. 
Pneumatolysis, defined. 234. 
Polybasite.' 825, 344. 368. 
Portland cement, see Cement. 
Posepny, on ore deposits, 246. 

on vadose water, 231. 
Potash, in soils, 214. 

Potsdam, irlass sand, 177; sandstone, 87. 
Pottery clay, defined, 99. 

distribution, 103. 
Pozzuolano, Italy, cement from, 111. 
Pratt, on chromite, 400. 

on chrysotile veins, 169. 

on corundum, 163. 
Pre-Cambrian, auriferous gravels, 327 ; clays, 

100 ; gold, 329 ; iron ores, 260. 
Precious stones, defined, 192. 

occurrence, 192. 

production, 195. 

references on, 195. 
Proctor, Tt., marble, 82. 
Proustite, 325. 
Psilomelane, 3S3. 

Pulpstones, properties and uses, 159. 
Tumice, 161. 

sources, 162. 



432 



INDEX 



Pumpelly, cited, 262. 
Pyrargyrite, 325. 
Pyrite, 286, 339, 371, 412. 

analysis, 199. 

as contact mineral, 235. 

distribution, Massachusetts, 199 ; New 
Tork, 199 ; Virginia, 199. 

in hot spring deposit, 228. 

occurrence, 199. 

references on, 200. 

uses, 200. 
Pyrolusite, 383. 
Pyromorphite, 303. 
Pyrope, as gem, 194. 
Pyrophyllite, composition, 203. 

North Carolina, 203. 

uses, 203. 
Pyroxene, as gangue mineral, 295. 
Pyrrhotite, 404. 

as contact ore, 235. 

Ducktown, Tenn., 295. 

in Virginia pyrite deposits, 199. 

Sudbury, Ont., 405. 

Q 

Quarries, bedding planes in, 74. 
Quarrying, structural features affecting, 74. 
Quarry water, 73. 
Quartz, crystalline, uses, 163. 

in kaolin, 100. 
Quicksilver, 390, 391, 393. 
Quincy, Mass., granite, 77. 

E 

Eealgar, 398. 

Bed Sulphur Springs, Va., 205. 

Eegolith, 213. 

Eeplacement, denned, 233. 

Eesidual soils, 213. 

Eesiduum, petroleum, 42. 

Eetort clay, defined, 99. 

Ehigolene, 56. 

Ehode Island, coal field, 25 ; graphite, 179. 

Ehodium, with platinum, 407. 

Eico, Colo., 307. 

banded veins at. 237. 

zinc concentrates, 319. 
Eift, 74. 
Eoad materials, 217. 

clay, behavior under traffic, 217. 

gravel, characteristics, 217. 

methods of testing, 218. 

references on, 218. 

requisite qualities, 218. 

sand, characteristics, 217. 

shale, 217. 
Eock crystal, as gem, 195. 
Eock pressure, Orton on, 45. 
Eock salt, occurrence, 125. 
Eocky Mountain region, yield of silver, 
332. 

coal fields of, 30. 



Euby, properties, 193. 

Arizona, 193 ; North Carolina, 193 ; United 
States, 193. 
Euby silver, 325. 
Euthenium, with platinum, 407. 
Eutile, 413. 

S 
Salina, gypsum, 142 ; salt, 129.' 
Salines, 124. 

Sail Mountain, 6a., amphibole asbestos, 167. 
Salt, analyses of salt and brines, 131. 

analyses of sea waters, 124. 

association with gypsum, 126. 

distribution, California, 130 ; Kansas, 130 ; 
Louisiana, 129 ; Michigan, 129 ; New 
Tork, 127 ; Texas, 130 ; Utah, 130. 

extraction, 131. 

impurities, 126. 

occurrence in waters, 124. 

production, 132. 

references on, 134. 

rock, origin, 125. 

sources of, 124. 

uses, 132. 
San Bernardino Hot Springs, Calif., 204. 
Sandberger, on dissemination of metals, 226. 
Sandstone, 84. 

arkose, 85. 

Berea, 87. 

bluestone, 85. 

distribution, 86. 

flagstone, 85. 

general properties, 84. 

Potsdam, 87. 

varieties of, 85. 
Sandusky, Ohio, gypsum, 142. 
San Juan region, Colorado, gold-silver, 341. 
Sap, 73. 
Sapphire, 193. 

distribution, Montana, 193 ; North Carolina, 
193 ; Siam, 193. 

properties, 193. 
Sagger clay, defined, 99. 
Saucon Valley, Pa., zinc ores, 311. 
Scheelite, 414. 

Schrauf, on mercury origin, 393. 
Sea water, pyrite precipitation from, 225. 

limonite precipitation from, 225. 

manganese precipitation from, 225. 
Selvage, 237. 

Semi-bituminous coal, defined, 5. 
Senarmontite, 396. 
Sericite, 326. 
Serpentine, for building, 83. 

characteristics, 83. 

distribution, 84. 
Seward peninsula, Alaska, 357 ; tin in, 412. 
Shale, analysis of, 98. 
Shutes, 237. 
Siam, sapphire, 193. 
Siberia, emerald, 193 ; turquoise, 194. 
Sicily, sulphur, 191. 



INDEX 



433 



Siderite, 272, 373. 

distribution, Kentucky, 273 ; New York, 
273 ; Pennsylvania, 273. 

geologic distribution, 272. 

mode of occurrence, 272. 
Sienna, denned, 187. 
Silica, as an abrasive, 163. 

deposition from water, 393. 

effect on clay, 95. 

in iron ores, 252. 

in soils, 214. 
Silurian, manganese in, 387. 
Silver, Butte, Mont., 284. 

ores of, 325. 

production, 358. 

uses of, 357. 

with mercury, 393. 
Silver Cliff, Colo., analyses of mine waters, 

227. 
Silver glance, 325. 
Silver ores, classification, 327. 

distribution of, see Gold-silver. 

extraction, 329. 

geologic distribution, 329. 

mode of occurrence, 326. 

production of, 35S. 

references on, 360. 

secondary enrichment, 827. 

wall rocks, 326. 

weathering of, 327. 
Silver-lead ores, 364. 

assays of, 372, 373. 

distribution, Aspen, Colo., 367 ; Cceur 
d'Alene, Ido., 372; Eagle River, 
Colo., 369 ; Eureka, Nev., 373 ; Glen- 
dale, Mont., 373 ; Leadville, Colo., 
864; Neihart, Mont., 373 ; New Mex- 
ico, 373 ; Park City, Utah, 370 ; Red 
Mountain, Colo., 369 ; Rico.Colo.,369 ; 
South Dakota, 373 ; Ten Mile district, 
Colo., 369 ; Tintic district, Utah, 372. 

references on, 374. 
Silverton, Colo., 341. 
Slate, as mineral pigment, 187. 

quarrying, waste in, 89. 

uses, 89. 
Slates, for building, 87. 

bleaching of, 88. 

cleavage, 87. 

distribution, SS. 
Smithsonite, 303, 305, 310, 312, 319. 
Smut, of coal, 16. 
Soapstone, 201. 

in southern Appalachians, 201. 

See Talc. 
Soda, in soils, 214. 
Soda niter, properties, 136. 

references on, 136. 
Sodium sulphate, 136. 
Soils, 213. 

aeolian, 214. 

alkali in, 215. 

2f 



alluvial, 214. 

chemical properties, 214. 

defined, 213. 

distribution, 216. 

dune, 214. 

flocculated, 215. 

glacial, 214. 

loamy, properties, 215. 

loess, 216. 

marsh, 216. 

origin, 213. 

physical properties, 215. 

prairie, 216. 

puddled, 215. 

references on, 216. 

residual, 213. 

sandy, 215. 

structure, 215. 

subsoil, 216. 

temperature, 216. 

texture of, 215. 

transported, 213. 

volcanic, 214. 
Solenhofen, Bavaria, lithographic stone, 182. 
Solid bitumens, 57. 
South Carolina, monazite, 190 ; phosphate, 150 ; 

tin, 411. 
South Dakota, fire clay, 103 ; gold. 350 ; fuller's 
earth, 175 ; lithium, 1S3 ; Portland 
cement materials, 119 ; 6ilver-lead 
ores, 373 ; tungsten, 415. 
Specularite, as contact ore, 235. 
Sperrylite, 407. 
Spessartite, as gem, 194. 
Sphagnum, 3. 
Sphalerite, 303, 305, 811, 312, 313, 315, 319, 

372, 373. 
Spodumene, 1S3. 

Spurr, on magmatic segregation, 225. 
Stannite, 410. 

Stassfurth, Prussia, salt at, 126. 
Steamboat Springs, Nev., 392. 
Stephanite, 325, 344. 
Stevenson, on anthracite formation, 15. 
Stibnite. 336, 339, 396. 

in hot spring deposit, 228. 
Stoneware clay, analysis of, 98. 

defined, 99. 

distribution of, 103. 
Stream tin, 410. 

Strontian Island, celestite on, 201. 
Strontium, minerals containing, 200. 

references on, 201. 

uses, 201. 
Subcarboniferous, salt, 129 ; limestone for 

lime, 116 ; zinc, 314. 
Subsoil, 216. 

Sudbury, Ont., nickel, 405. 
Sulphides, in contact deposits, 235. 
Sulphur, distribution, Louisiana, 197 ; Japan, 
196; Mexico, 196; Oregon, 197; 
Utah, 196. 



434 



INDEX 



Sulphur — continued. 

geologic age, 197. 

gypsum type, 19T. 

in coal, 9. 

in copper ores, 280. 

origin, 197. 

production, 198. 

references on, 198. 

solfataric type, 196. 

uses, 198. 
Sussex County, N.J., zinc ores, 
Sweet Springs, W. Va., 204. 
Sylvanite, 325, 339. 



Table Mountain, Calif., 347. 
Talc, 201. 

analyses of, 202. 
as alteration product, 201. 
distribution, New York, 202 ; North Caro- 
lina, 201. 
origin and occurrence, 201. 
production, 203. 
references on, 203. 
uses, 202. 
Tellurides, 325. 

unknown in contact deposits, 235. 
Tellurium in copper, 280. 
Tennantite, 285. 

Tennessee, ball clay, 103; barite, 170; fluor- 
spar, 173 ; Jellico coal, analysis of, 7 ; 
garnet, 163 ; phosphate, 150 ; stone- 
ware clay, 103. 
Terlingua, Texas, mercury, 392. 
Terra alba, 143. 
Terra-cotta clay, denned, 99. 
Tertiary, fuller's earth, 175; gold-silver ores, 
337; glass sand, 177 ; greensand, 155 ; 
lignite, 19 ; limonite, 271 : phosphates, 
148, 153 ; sulphur, 197. 
Tetrahedrite, 278, 285, 297, 321, 331, 339. 
Texas, bat guano, 155 ; bituminous coal, analy- 
sis, 7 ; coal, 29 ; fuller's earth, 175 ; 
gypsite, 142 ; lignite, 6, 30 ; lime rock, 
116 ; limonite, 271 ; mercury, 392 ; 
natural gas, 56 ; petroleum, 51 ; Port- 
land cement materials, 119 ; salt, 130 ; 
stoneware clay, 103. 
Thermal springs, origin, 204. 
Thorium, in monazite, 190, 191. 
Tin, association with granite, 226. 

distribution, Alaska, 412 ; Black Hills, 411 ; 
Malay Peninsula, 412 ; North Caro- 
lina, 411 ; South Carolina, 411. 
mode of occurrence, 410. 
ores, 410. 

production of, 412. 
references on, 413. 
uses of, 412. 
Titanic acid, in clay, 96. 

Titanium, distribution, Norway, 413 ; Penn- 
sylvania, 414 ; Virginia, 414. 



in iron ores, 252. 

occurrence, 413. 

ores, 413. 

references on, 414. 

uses, 414. 
Tonopah, Nev., 343. 

Topaz, distribution, Brazil, 194 ; California, 
194; Ceylon, 194; Colorado, 194; 
Maine, 194 ; Urals, 194. 

properties, 194. 
Torbanite, 57. 
Tourmaline, as gem, 195. 

with tin, 412. 
Transported soils, classification, 214. 

origin, 213. 
Trap, 78. 

Travertine, defined, 80. 
Trenton, limestone for lime, 116; petroleum 

in, 51. 
Triassic, coal, 25 ; magnetite, 256. 
Trinidad, asphalt in, 59. 

analysis of, 60. 
Tripoli, see Infusorial earth. 
Tully limestone, for Portland cement, 118. 
Tungsten, analysis, Arizona, 415. 

distribution, Arizona, 415 ; Black Hills, 415 ; 
Colorado, 415 ; Connecticut, 415 ; 
Nevada, 415. 

ores, 414. 

production, 415. 

references on, 416. 

uses, 415. 
Turquoise, distribution, Arizona, 194 ; Asia 
Minor, 194 ; New Mexico, 194 ; Per- 
sia, 194 ; Siberia, 194. 

properties and occurrence, 194. 
Type metal, 397. 

U 
Uintaite, 59. 
Ulexite, 134. 
Umber, defined, 187. 
Underground waters, 207. 
references on, 211. 
sources of, 207. 
Urals, topaz in, 194. 

Uranium, distribution, Colorado, 416; Utah, 
416. 
ores, 416. 
production, 416. 
references on, 417. 
uses, 416. 
Utah, coal, 31 ; copper, 296 ; desilverized lead, 
307 ; hematite, 268 ; magnetite, 256 ; 
manganese, 388 ; molybdenum, 403 ; 
Portland cement materials, 119 ; salt, 
130 ; silver-lead ores, 372 ; sulphur, 
196 ; uranium, 416. 



Vadose water, defined, 227. 
Vanadium, distribution, Arizona, 416 ; New 
Mexico. 416. 



INDEX 



435 



Vanadium — continued. 
ores, 416. 
production, 416. 
references on, 417. 
uses, 416. 
Tan Hise, on Lake Superior ores, 262. 
on meteoric waters, 22S. 
on ore deposit classification, 246. 
Veins, see Fissure veins. 
Vermilion, as mineral pigment, 188. 
Vermilion Range, Minn., 261, 264. 
Vermont, asbestos, 168 ; marble, 82 ; whet- 
stones, 160. 
Vesuvianite, in contact deposits, 235. 
Yirgilina, Va., copper, 291. 
Virginia, arsenic, 398 ; asbestos, 167 ; barite, 
170 ; brines, 129 ; coal, 25 ; green- 
sand, 155; gypsum, 142; infusorial 
earth, 162 ; kaolin, 101 ; limonite, 
271 ; pyrite, 199 ; titanium, 414. 
Virginia City, New, 344. 
Vogt, on magmatic segregation, 224. 
Volcanic ash, 161. 

United States deposits, 162. 
soils, 214. 

W 
Wad, 383. 

Warm Springs, Tenn., 204. 
Warm Sulphur Springs, Va., 205. 
Washington, arsenic, 39S ; bituminous coal, 
analysis of, 8 ; coals, 32 ; gold, 335 ; 
lignite, analysis, 6; molybdenum, 
403 ; nickel, 404. 
Water, artesian, 209. 

as carrier of ores, 226. 

circulation of meteoric, 229. 

distribution in earth's crust, 228. 

hot, agent in ore formation, 22S. 

in clay, 96. 

mine, analyses, 227. 

mineral, 205. 

of igneous origin, 229. 

of meteoric origin, 228. 

underground, source of, 228. 
Water lime beds, cement rock in, 117. 
Water table, 20S. 

Watson, on Georgia manganese, 386. 
Weathering, building stones, 70, 75, 79, 85. 

ore deposits, 242. 
Weed, cited, 22S. 230, 246. 



West Virginia, brines, 129 ; gas, 55 ; glass sand, 

177 ; grahamite, 59 ; natural gas, 55 ; 

petroleum, 48. 
Westerly, E.I., granite, 77. 
Whetstones, defined, 159. 

distribution, 160. 
White, I. C, on anticlinal theory, 43. 
White lead, as mineral pigment, 188. 
White metal, 320. 
Whiting, as mineral pigment, 1SS. 
Whitney, on Lake Superior ores, 262. 
Willemite, 303, 304, 30S, 310. 
Winslow, on Missouri lead and zinc. 226. 
Wisconsin, Clinton ore, 266 ; graphite, ISO ; 

hematite, 261, 264 ; limomite, 271 ; 

natural rock cement, US; zinc ores, 

312. 
Wolframite, 414. 
Wollastonite, 235. 
Wulfenite, 403. 
Wyoming, asbestos, 168 ; copper, 298 ; gypsite, 

142 ; hematite, 268 ; magnetite, 256 ; 

nickel, 404; petroleum, 53; platinum, 

408. 

Y 
Yellow ocher, see Ocher. 
Yukon valley, Alaska, 353. 



Zinc, Butte, Mont., 285. 
ores of, 303. 
production of, 321. 
with mercury, 393. 
uses of, 320. 
Zincite, 303, 30S, 310. 
Zinc ores, analysis of, Leadville, 318. 
Missouri, 815. 
New Jersey, 308. 
distribution, Creede, Colo., 319 ; Iowa, 311 ; 
Missouri, 314 ; New Jersey, 30S ; New 
Mexico, 319 ; Pennsylvania, 311 ; Vir- 
ginia-Tennessee, 309 ; Wisconsin, 311. 
impurities in, 304. 
mechanical concentration, 313. 
references on, 323. 
residual, 310. 
superficial alteration, 305. 
Zinc oxide, manufacture in Colorado, 318. 
Zone of flowage, 22S. 
Zone of fracture, 228. 



ELEMENTARY GEOLOGY. 



BY 



RALPH STOCKMAN TARR, B.S., F.G.S.A., 

Professor of Dynamic Geology and Physical Geography at Cornell University; 
Author of "Economic Geology of the United States" etc 



tamo. Cloth. 486 pp. Price $1.40 net. 



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plest high-school text-book on the market. 



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ELEMENTARY PHYSICAL 
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Professor of Dynamic Geology and Physical Geography at Cornell University; 
Author of " Economic Geology of the United States," etc. 



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